An FBI investigation into the Clinton Foundation is advancing rapidly - unless the Justice Department interferes, two sources familiar with the probe told Fox News.

The Clintons are accused of running a pay-for-play operation out of the State Department that favored donors to their charity - a charge they have denied.

But the feds are 'actively and aggressively pursuing this case,' Fox's Brit Hume and Bret Baier reported Wednesday, and they have an 'avalanche' of evidence.

A Wall Street Journal report says the FBI's pursuit of the case is rooted in recordings of a suspect in a different corruption case who spoke about the Clinton Foundation's alleged dirty dealings.

Hillary Clinton boards her campaign plane at Phoenix Sky Harbor International Airport in Phoenix today. Coincidentally, she was taking off from the same airport that her husband met Loretta Lynch at in June for a tete-a-tete that caused headaches for both sides.

The FBI, lead by James Comey, is 'actively and aggressively pursuing this case,' the sources said. Attorney General Loretta Lynch's Justice Department keeps telling the FBI to stand down, a second report revealed

The FBI's pursuit of the case is rooted in recordings of a suspect in a different corruption case who spoke about the Clinton Foundation's alleged dirty dealings

The FBI, under the leadership of director James Comey, believed those conversations were enough to move forward with the probe, the Journal says. Justice Department prosecutors disagreed because the source was not an employee of the Clinton Foundation.

They considered the talk to be hearsay and did not think it would be enough to sway a grand jury.

Fox is now reporting that federal investigators have collected 'a lot of' evidence, including Wikileaks emails to and foundation officials.

The law enforcement agency has at least four other investigations open that involve the Clintons and their close friends, as well.

The FBI's probe into the foundation is much larger than has previously been reported, the network says. Some witnesses are being interviewed for a third time.

It is a 'very high priority,' Fox's sources said.

The Journal says that as recently as August 12 the FBI was told to stand down by DOJ in a terse phone call.

'Are you telling me that I need to shut down a validly predicated investigation?’ the FBI's deputy director Andrew McCabe reportedly replied. The Justice Department official on the other end of the line said, 'Of course not.'

That was before Wikileaks began publishing hacked emails from Clinton confidante John Podesta's account ripping the lid off foundation operations.

McCabe's wife's Virginia senate campaign was backed heavily by a political action committee belonging to the Clintons' close friend Terry McAuliffe. Hillary Clinton headlined a fundraiser for the PAC, Common Good VA, a month before it started donating to the FBI official's spouse.

The McAuliffe PAC gave Jill McCabe $467,000 for her losing bid. The Virginia Democratic Party donated another $207,788 to her. All told, McCabe received $675,000 from the two entities.

Andrew McCabe was promoted to his current position at the FBI in February, around the time the bureau and DOJ began to butt heads over the Clinton Foundation.

Republicans have suggested McCabe went too soft on Clinton in her email investigation, which ended last summer without an indictment but restarted last week as new messages were uncovered, because of their personal connection.

House Oversight Committee chairman Jason Chaffetz reportedly asked McCabe to recuse himself from the case.

The Wall Street Journal's reporting indicates that the Justice Department, led by Attorney General Loretta Lynch, is holding up the Clinton Foundation probe.

In February, the FBI presented its case to DOJ public-integrity prosecutors. Lawyers at the Justice Department thought the case against the Clinton Foundation was too weak.

'The message was, "We’re done here," ' a Journal source said.

This email from Peter Kadzik to John Podesta started a new WikiLeaks firestorm, and Trump wasted no time in weighing in

Donald Trump predicted Thursday that President Barack Obama's administration would ultimately decline to prosecute the former cabinet secretary.

'The system is rigged. Just remember that,' he said Thursday in Jacksonville, Florida. 'Reports also show the political leadership at the Department of Justice is trying to protect Hillary Clinton, and is interfering with the FBI's criminal investigation.'

Trump accused Clinton of engaging in 'massive, far-reaching criminal conduct, and equally far-reaching cover-up.'

'She engaged in corrupt pay-for-play at the State Department for personal enrichment. She lied to the FBI and she lied to the American people many, many times,' he said.

The attorney general came under scrutiny over the summer as the FBI finished its review of Hillary Clinton's emails and home brew server for allowing Bill Clinton to board her plane in Phoenix, Arizona.

She says the department's inspection of Mrs. Clinton did not come up during their tarmac talk. The perception of impropriety was enough for her to back away from the Clinton case and say she would accept the FBI's final recommendation at face value.

The American Center for Law and Justice (ACLJ) believes there's more to the story and is suing for more information about her June 27 meeting with Bill at the Phoenix Sky Harbor International airport.

Hillary Clinton's campaign chairman John Podesta (left) once boasted that Peter Kadzik (right), Podesta's attorney during the Lewinsky years, kept him out of jail

Another DOJ official with longstanding ties to Podesta - he was the former Bill Clinton chief of staff's lawyer during the Monica Lewinsky scandal - was caught in Wikileaks emails giving his friend a 'heads up' on a congressional hearing on Clinton's server.

'There is a HJC [House Judiciary Committee] oversight hearing today,' Peter Kadzik wrote in 2015, 'where the head of our Civil Division will testify.'

The assistant attorney general told Podesta the DOJ lawyer testifying was 'likely to get questions on State Department emails.

'Another filing in the FOIA [Freedom Of Information Act] case went in last night or will go in this am that indicates it will be awhile (2016) before the State Department posts the emails.'

Podesta copied another senior campaign staffer on a response email that said the hearing would provide 'additional chances for mischief.'

Kadzick was the same DOJ official who provided lawmakers with a statement this week on the FBI's examination of the new Clinton emails.

South Carolina Republican Rep. Trey Gowdy, chairman of the House's Benghazi committee, told Fox he has 'many differences' with the Justice Department official, but he isn't worried about a conflict of interest.

'Peter Kadzik is not a decision maker, he is a messenger,' Gowdy assessed.

The FBI's investigation into the Clinton Foundation is just one of five its pursuing that directly or indirectly involves former President Bill Clinton and his wife, the Democratic nominee for the White House.

A probe of Anthony Weiner's sexts to a 15-year-old led the FBI to stumble upon new emails from his estranged wife Huma Abedin's account that linked back to the original, Clinton classified information review. Comey said last week that he authorized agents to reconsider that case as it reviews the recently discovered emails.

The FBI is also looking at a $120,000 donation that ex-Clinton aide and Virginia Gov. Terry McAuliffe received from a Chinese businessman who has given to the Clinton Foundation in the past.

Lobbyist Tony Podesta, co-founder of the Podesta Group, a shop he started with his brother John, the chairman of Clinton's presidential campaign, is caught up in an investigation of a corrupt Ukrainian politician his firm advised.

Tony Podesta is also a bundler for the Clinton campaign.

The progress of the Clinton Foundation investigation and the one into McAuliffe were first reported by the Wall Street Journal.

The FBI does not generally comment on investigations, so it is possible there are more under way.

FIVE FBI INVESTIGATIONS: HOW CLINTON'S INNER CIRCLE ARE CAUGHT UP IN WEB OF 'CRIME' PROBES WHICH THREATENS TO SHADOW HER IF SHE WINS

Almost all of Clinton's inner circle - the cast of advisers known as Clintonworld - and many of their family are caught up in an FBI dragnet.

The scale of investigations under way is unprecedented in electoral history.

There are five separate investigations:

The handling of classified information on the Clinton email server

Whether the Foundation was used to peddle influence

Whether illegal Chinese donations were taken by a Clinton intimate

Whether John Podesta's brother acted as a front for illegal lobbying

Anthony Weiner's sexting relationship with a 15-year-old.

Here we examine who is caught up and how.

What does she know: Huma Abedin has been Clinton's shadow for 20 years but now finds herself off the campaign trail and facing new FBI interest

Huma Abedin: secrets and access - and perjury?

Probes: Clinton emails; Clinton Foundation

Who is she: Currently vice-chair of the Clinton campaign she was has worked with Clinton for 21 years, since she was 19, as among other things, intern, 'body woman', chief of staff and senior adviser.

Huma Abedin is now represented by attorneys as the FBI begins the lengthy process of examining a laptop seized in the inquiry into her estranged husband's sexting relationship with a 15-year-old.

It is the most recent stage in the Clinton emails investigation in which the FBI has looked into whether Clinton and her staff broke strict laws on the handling of classified material while she was Secretary of State through their use of the now notorious Clintonemail.com server.

The case appeared to be closed in July when James Comey, the FBI director announced that Clinton would not be prosecuted. It was later made clear there would be no other prosecutions.

However last week's bombshell announcement that new emails were being examined put the focus squarely on 40-year-old Abedin.

Although the decision had been made not to prosecute, that was on the basis of the existing evidence at the time. But if the search finds new evidence of breaking laws about the handling of classified material, there is nothing to stop a prosecution of Abedin - or anyone else.

That, however, is not the only potential for a brush with the law for Abedin.

The FBI investigation into the Clinton Foundation also drags her into the spotlight.

The probe, the Wall Street Journal reported, is into whether the Foundation was involved in financial crimes or influence-peddling.

That would directly draw in Abedin. Her overlapping series of roles while Hillary Clinton was Secretary of State has been unmasked by emails published either as a result of lawsuits against the State Department, or hacked from John Podesta's account.

She was at various times Clinton's White House deputy chief of staff; her senior adviser; a consultant for Teneo Holdings; working for the Clinton Foundation.

It was also revealed that while she was at the State Department where she was Clinton's gatekeeper, Abedin received emails from Doug Band - Bill Clinton's right-hand man at the Clinton Foundation - asking for help and access for 'friends' or 'friend of ours'.

And finally there is the possibility of a federal perjury case.

The discovery of a laptop during the Anthony Weiner sexting investigation by the FBI appears at odds with testimony she gave under oath as part of a deposition in a federal case that she had passed on all relevant devices to the FBI.

Best of friends: Virginia governor Terry McAuliffe with Hillary Clinton as she headlined a fundraiser for the PAC he controls. It then gave $500,000 to the wife of the now FBI deputy director for her own political ambitions

Terry McAuliffe: Clinton cash from China

Probes: Clinton Foundation; links to foreign donations

Who is he: Currently Democratic governor of Virginia. Has previously been prolific Clinton fundraiser and chairman of the Democratic National Committee, and chairman of Hillary's failed 2008 run for the White House.

McAuliffe was a board member of the Clinton Foundation from at least 2004, so he will surely be caught up in investigations conducted by the FBI's Washington DC field office into whether it was used as a front for influence-peddling.

But the overlaps between him and the Foundation go further than that and into his own campaign for governor and related campaigning.

The Washington Post reported in 2015 how he and the foundation had 120 overlapping donors, who had given him, his campaign or his political action committee $13.8 million.

That political action committee then went on to fund another campaign - that of Dr Jill McCabe, whose husband Mark is currently the deputy director of the FBI. He was the assistant FBI director when Jill McCabe was running for state senator in Virginia.

The PAC controlled by McAuliffe, which had received money from Clinton Foundation donors, gave Jill McCabe more than $500,000, prompting her husband to stand back from the Clinton Foundation investigation.

Chinese government front? Wang Wenliang, the billionaire McAuliffe at first claimed he had never met, filmed entering a fundraiser attended by the governor at Clinton's home

Part of the $13.8 million is, however, involved in a second FBI investigation which focuses on McAuliffe personally regarding donations of $120,000 from a Chinese man called Wang Wenliang.

The FBI is investigating whether donations made were in breach of a ban on foreign governments influencing US elections. Wenliang, a billionaire according to Forbes, is a member of the one-party state's parliament - as well as a donor to the Clinton Foundation.

He is also a US permanent resident and his donations came through a US firm.

This weekend's tidal wave of revelations also shed new light on an FBI investigation into the donations.

McAuliffe's attorney was reported by the Wall Street Journal to have said that the investigation focused on whether he had previously failed to register as an agent of a foreign entity.

In May, when the revelation of the FBI foreign donations probe emerged, McAuliffe denied ever meeting Wenliang. Then he backtracked - saying 'I did not deals' - when told by his staff that there were 'likely' several meetings.

DailyMail.com revealed footage of him going to a fundraiser also attended by Wengliang.

The venue was Hillary Clinton's Washington DC home and the attendees included Huma Abedin.

The governor's lawyer told the Wall Street Journal the probe is focused on 'whether he failed to register as an agent of a foreign entity'.

Cheryl Mills: Woman at center of Clintonworld

Cut a deal: Cheryl Mills gained partial immunity from the FBI in return for opening her laptop

Probes: Clinton Foundation; Clinton emails

Who is she: Long-term Clinton lawyer who advised Bill during impeachment then Hillary over emails; Foundation director; State Department chief of staff.

Cheryl Mills is unusual among Clinton insiders; she has already cut a deal with the FBI.

She exchanged partial immunity from prosecution in return for opening her laptop to FBI review during the Clinton email investigation.

Mills was chief of staff under Clinton at the State Department and communicated extensively on the Clintonemail.com private server.

The deal with the Justice Department - headed by Attorney-General Loretta Lynch - was hugely advantageous as it also limited the search to no later than January 31, 2015, the point at which the server's existence became known to a Congressional committee.

In March backups of Clinton's emails were destroyed by a technician, a move which could have been seen as illegal destruction of evidence.

And the deal allowed for the destruction of Mills' laptop. Heather Samuleson, another more junior aide, cut the same deal.

Mills went on to sit in with Clinton on her FBI interview in early July as her attorney, an unusual arrangement given that she had previously been a focus of the investigation.

However the renewed move by the FBI to examine the Huma Abedin emails on the Weiner laptop could set the immunity aside.

If they find new emails, those could open the way for prosecution. Equally, if they examine emails already seen on her laptop and conclude that they represent a case for prosecution over the handling of classified material, that too would be unlikely to be covered by the immunity deal.

Foundation role: Cheryl Mills was deeply involved in the Clinton family charity during a war between Chelsea and Doug Band, her father's right-hand man

In fact, any part of Mills' role in setting up the server could now be back in play. She was clearly identified in one of the Wikileaks emails as part of the reason for secrecy around Clinton.

That is only one of Mills' roles in Clintonworld which the FBI are concerned with.

The other is her role as director of the Clinton Foundation for two periods, 2004 to 2009 and then from 2013 on.

The influence-peddling investigation has not been the subject of public commentary by the FBI but would involve anyone who held a high-level role.

Mills was heavily involved in the Foundation not just as a director, but while she was working at the State Department.

During that time it was at the center of a fierce battle between Chelsea Clinton and Doug Band, in which Band was effectively forced out.

Mills drew up a new structure for all of Bill Clinton's operations - at the time it was the William J. Clinton Foundation - and, Wikileaks publication of John Podesta's email shows - took part in a number of exchanges about it.

The State Department has previously said that Mills paid her own way to go to Clinton Foundation meetings in New York.

But neither the department nor the Clintons have addressed whether the FBI is looking at whether the Clinton Foundation monetized access to the Secretary of State through the overlapping roles of, among others, Mills and Abedin.

At her side: Phillipe Reines was effectively Hillary Clinton's chief spin doctor when she was Secretary of State - the point at which the email and Foundation probes center on

Phillipe Reines: What does he know of emails and access?

Probes: Clinton emails; Clinton Foundation

Who is he: Hillary Clinton press secretary when she was senator; press secretary to failed 2008 presidential campaign and spokesman for Chelsea during it; Deputy Assistant Secretary of State for Hillary; played Donald Trump in debate prep.

As one of her inner circle at the State Department, Phillipe Reines was one of those - he told the FBI - who Clinton turned to for help with her IT issues.

He also bought her an iPad in June 2010, when the technology was new.

Clinton was to go on to claim she only had 'one device'. Reines meanwhile used both his state.gov email and his personal gmail for government business while in office.

Reines was also deeply involved in responding to the Benghazi committee's demands for information about the server and the public relations response to it, Wikileaks emails from John Podesta's gmail have revealed.

However the other Clinton Foundation probe could also drag in Reines.

Reines was a key member of the inner circle when Clinton was Secretary of State.

His official title was 'deputy assistant undersecretary' for strategy, effectively her most powerful public affairs adviser.

That means that any knowledge he has of how the Clinton machine in the State Department interacted with the Clinton Foundation and Bill Clinton Inc machines in Manhattan would be crucial to the FBI investigation

Key role at center of the Clinton web: John Podesta, whose leaked emails were leaked. He took the helm of the Clinton Foundation, which is being probed on whether it peddled access

John Podesta: 'Dean' of Clintonworld

Probes: Clinton Foundation

Who is he: Bill Clinton's first White House deputy chief of staff and later chief of staff; founder of DC lobbying firm Podesta & Podesta, now the Podesta Group; took charge of the Clinton Foundation in 2011 ; now Hillary campaign chairman; at 67, often seen as the 'dean' of the Clinton political machine.

The leaks from John Podesta's emails revealed by Wikileaks have shown how he was a key player in the Clinton Foundation - at precisely the time that the focus of the FBI influence-peddling investigation is likely to be.

At the time Clinton was Secretary of State and Doug Band, who had effectively run the foundation, wrote a memo which emerged in Podesta's leaked emails.

In it, Band detailed the overlap between the commercial activities of Bill Clinton and the charitable fundraising of the William J. Clinton Foundation (now the Clinton Foundation) - material which is likely to be pertinent to the influence-peddling case.

Podesta's role at Foundation lasted into 2012, so his knowledge of how it interacted with Hillary Clinton's aides - particularly Cheryl Mills, with whom he was in frequent contact, according to the emails - would be relevant to the FBI probe.

Lobbyist: Tony Podesta is the brother of Clintonworld 'dean' John Podesta but is being investigated by the FBI over taking a contract from a firm which may have been a front for corrupt cash from Ukraine's deposed president Viktor Yanukovych - an ally of Vladimir Putin

Tony Podesta: Dined with Hillary, lobbied for Putin's ally?

Probe: Undeclared lobbying for foreign government

Who is he: Older brother of John Podesta, with whom he founded what is now The Podesta Group of which he is chairman; social acquaintance of the Clintons; Democratic fundraiser

The FBI and the Justice Department are investigating possible ties to alleged corruption involving the former president of Ukraine - and Podesta's firm is one of those targeted.

Perhaps surprisingly, the investigation also lapped at the Trump campaign, as its then chairman Paul Manafort stepped down in August when it was revealed that his company was also being investigated.

The broad-based investigation is looking into whether U.S. companies and the financial system were used to enable corruption by the party of former pro-Russian Ukrainian president Viktor Yanukovych, CNN reported.

The Podesta Group hired an independent legal firm to investigate whether it had been misled by the Center for a Modern Ukraine, a not-for-profit group linked to the ousted Ukrainian government, a spokeswoman for the group said in a statement to Reuters in August.

The key to the FBI investigation is that Manafort and his deputy Rick Gates may have been paid by the Yanukovych government to push its case in Washington without declaring that the money came from abroad.

One of the firms Gates appears to have hired to help push the Center for a Modern Ukraine was The Podesta Group.

The FBI will therefore look at whether Podesta knowingly or negligently breached laws requiring all foreign attempts to influence U.S. politics to be registered.

Yanukovych was ousted as Ukranie's leader in 2014 - and is exiled in southern Russia, after long-term accusations that he was a friend of Vladimir Putin.

The older Podesta, his brother's emails disclosed, remains extremely close to John, sharing the use of an apartment in New York until earlier this year. Official records also show he is a 'bundler' for Clinton who had raised $62,000 by the end of June.

It is a long-standing relationship. One email forced out of the State Department showed how in 2012 the Clinton Foundation used the then Secretary of State to host a dinner at her home where attendees included donors - and Podesta.

Body man: Doug Band was Bill Clinton's personal aide at the White House but went on to effectively run the Foundation - then boasted in a leaked memo of making the ex-president rich

Doug Band: Man who made Bill rich

Probe: Clinton Foundation

Who is he: Bill Clinton's 'body man' in the White House; his chief aide after leaving office until 2011; CEO of Teneo Holdings.

The FBI investigation into whether the Clinton Foundation committed financial crimes or was involved in influence-peddling will inevitably focus on one man in particular: Band.

Band was at Bill Clinton's side to the same extent as Huma Abedin was at his wife's, starting as his 'body man' in the White House, putting himself through law school in the evenings, and then running Bill Clinton's post-presidency life.

His emails to Cheryl Mills and Huma Abedin which have emerged in lawsuits forcing publication by the State Department show how he sent messages asking for meetings for people described as 'friend' or 'good friend of ours'.

Any influence-peddling or financial crimes committed by the Foundation appear to have some connection to them, if they were to exist.

His explosive memo detailing the project to make Bill Clinton rich which he sent to John Podesta made clear how involved he was in 2011 in the Clintons' lives and finances.

'Independent of our fundraising and decision-making activities on behalf of the Foundation, we have dedicated ourselves to helping the President secure and engage in for-profit activities – including speeches, books, and advisory service engagements,' he wrote.

'In that context, we have in effect served as agents, lawyers, managers and implementers to secure speaking, business and advisory service deals.'

It also put a figure on Bill Clinton's personal gains via Band.

'Since 2001, President Clinton’s business arrangements have yielded more than $30 million for him personally, with $66 million to be paid out over the next nine years should he choose to continue with the current engagements,' it said.

His current exact status in the Clinton inner circle appears unclear. On the one hand he has not been pictured with the Clintons in many years or listed at their events.

On the other hand, he continues to donate to the Clinton cause and to those of its allies - he was one of the donors to Virginia governor Terry McAuliffe's PAC which was used to pay $500,000 to the FBI assistant director's wife for her failed campaign bid.

And in 2013 he asked John Podesta to help remove any stain on his reputation with a glowing letter of reference. Podesta obliged by redrafting it for him.

Inner circle: Justin Cooper set up the Clinton email server and edited Bill's autobiography - but the FBI is also looking into the Foundation he was involved in

Justin Cooper: Smashed BlackBerry with a hammer

Probes: Clinton Email; Clinton Foundation

Who is he: Staff assistant for Oval Office operations in Bill's White House; Doug Band's right-hand man; edited Bill's memoir My Life; registered the notorious Clintonemail.com server; now works for Teneo with Band.

Justin Cooper's role in the Clintonemail.com secret server started at the very beginning of its operation: he registered its existence.

At the time he was being paid by the Clintons as a family aide and through the Clinton Foundation.

He told one Congressional Committee - the Oversight and Government Reform Committee - that he had no security clearance.

However as the man with complete control over the server, he had unlimited access to its contents. He also destroyed devices which had been linked to the server, including a BlackBerry smashed with a hammer.

He was not prosecuted under the initial inquiry but if the Huma Abedin-Anthony Weiner record leads to new evidence, such a deal would be off the table.

He was also at the very center of the Foundation's operations during much of the time Hillary Clinton was in office.

He frequently appears in the leaked John Podesta emails as 'justin@presidentclintonoffice.com' and is involved in a series of key meetings.

That would make him a key focus for the other investigation into the foundation he was so intimately involved in was a front for influence-peddling or financial crimes.

Unhappy together: Huma Abedin and Anthony Weiner were seen on the day DailyMail.com revealed he had sexted a 15-year-old girl, setting off the explosive chain of events leading to the renewed FBI probe

Anthony Weiner: Sexual sleaze

Probe: Sexting 15-year-old girl

Who is he: Former New York congressman when Clinton was senator; estranged husband of her key aide Huma Abedin; notorious serial sexter.

The FBI probe into Anthony Weiner is unlike any of the other Clinton associates and their family members.

Weiner is being investigated after DailyMail.com revealed how he had had a sexting 'relationship' with a 15-year-old girl who told him he was underage.

Notorious image: This is the picture Weiner sent a girl, 15, which was part of the DailyMail.com bombshell which prompted the FBI probe

The girl told DailyMail.com that Weiner spoke about rape fantasies with her. She showed messages in which he spoke about being 'hard' and how he 'would bust that tight p****'.

The revelations came a month after Abedin had announced that her six-year-old marriage to him was over when he was caught sexting a woman in her 40s to whom he sent a picture of himself in bed, apparently aroused, with his son by Clinton's chief aide sleeping by his side.

The FBI moved on Weiner in the wake of the DailyMail.com revelations and seized all his mobile and electronic devices.

It was on a laptop he had used that they found emails 'relevant' to the discontinued Clinton email server investigation - setting off a bomb under the presidential election.

Weiner's computer was apparently being searched for child pornography at the time of the discovery.

The FBI now have a fresh search warrant which will allow them to examine the material found on the laptop which had apparently been stored by Huma Abedin.

The material could impact almost every one of the investigations listed by DailyMail.com.