The U.S. attorney appointed to examine the origins of the Russia investigation has been working on his review “for weeks,” a person familiar with the process told Fox News on Tuesday, to probe "all intelligence collection activities" related to the Trump campaign during the 2016 presidential election.

Fox News reported on Monday that Attorney General Bill Barr had assigned John Durham, the U.S. attorney in Connecticut, to conduct the inquiry into alleged misconduct and alleged improper government surveillance on the Trump campaign in 2016 as well as whether Democrats were the ones who improperly colluded with foreign actors.

BARR ASSIGNS US ATTORNEY IN CONNECTICUT TO LOOK INTO GOVERNMENT SURVEILLANCE INVOLVING TRUMP CAMPAIGN

Durham, known as a “hard-charging, bulldog” prosecutor, according to a source, will focus on the period before Nov. 7, 2016—including the use and assignments of FBI informants, as well as alleged improper issuance of Foreign Intelligence Surveillance Act (FISA) warrants. Durham was asked to help Barr to "ensure that intelligence collection activities by the U.S. Government related to the Trump 2016 Presidential Campaign were lawful and appropriate."

A source also told Fox News that Barr is working "collaboratively" on the investigation with FBI Director Chris Wray, CIA Director Gina Haspel, and Director of National Intelligence Dan Coats, and that Durham is also working directly with Justice Department Inspector General Michael Horowitz, who is currently reviewing allegations of misconduct in issuance of FISA warrants, and the role of FBI informants during the early stages of the investigation.

Meanwhile, President Trump on Tuesday praised Barr for appointing Durham and maintained that he did not request that the attorney general do so.

"I think it's a great thing that he did it," Trump told reporters from the White House lawn Tuesday. "I am so proud of our attorney general that he's looking into it."

Durham has led numerous public corruption probes, including organized crime, government misconduct and financial fraud matters. In 1999 AG Janet Reno appointed Durham to investigate law enforcement corruption in Boston, and under AG Eric Holder Durham was selected to investigate matters relating to the destruction of videotapes by the CIA and treatment of detainees by the CIA.

Barr first announced that he was reviewing the “conduct” of the FBI’s original Russia investigation during the summer of 2016 last month, following calls from Republicans, and President Trump, to investigate the origins of the probe.

“I am reviewing the conduct of the investigation and trying to get my arms around the aspects of the counterintelligence investigation that was conducted in the summer of 2016,” Barr testified on April 9.

That same day, Fox News learned that Barr had assembled a “team” to investigate the origins of the investigation. A source told Fox News Tuesday that Durham has been working on the investigation “for weeks,” but it is unclear if he was part of the original team assembled by Barr last month.

The FBI’s July 2016 counterintelligence investigation was opened by former senior agent Peter Strzok. Former FBI counsel Lisa Page, with whom Strzok was romantically involved, revealed during a closed-door congressional interview that the FBI “knew so little” about whether allegations against the Trump campaign were “true or not true,” at the time that they opened the probe, noting that they had just “a paucity of evidence because we are just starting down the path” of vetting the allegations. Page later said that it was “entirely common” that the FBI would begin a counterintelligence investigation with just a “small amount of evidence.”

The FBI, at the time, was led by former Director James Comey and former Deputy Director Andrew McCabe—both fired during the Trump administration.

It has been widely reported that in the weeks and months leading up to the 2016 election, the FBI employed informants to probe and extract information from Trump campaign officials.

Earlier this month, The New York Times reported that an investigator working for the U.S. intelligence community posed as a Cambridge University research assistant in September 2016, and tried to probe former Trump foreign policy adviser George Papadopoulos on the campaign’s possible ties to Russia.

The investigator, who went by Azra Turk, met with Papadopoulos at a London Bar, where she asked directly whether the Trump campaign was working with Russia. Papadopoulos told Fox News that he saw Turk three times in London: once over drinks, another time over dinner, and then once with Stefan Halper, the Cambridge professor who had been a longtime FBI informant. The Times noted that Turk had apparently been sent to oversee Halper, and possibly provide cover for Halper in the event Turk needed to testify.

Papadopoulos told Fox News earlier this month that he “immediately thought she was an agent, but a Turkish agent, or working with the CIA,” and explained “that’s why I never accepted her overtures and met her again after London…London became a very bizarre hangout spot for me that year.”

Papadopoulos also told Fox News that Turk was trying to “seduce” him in an effort to “make me slip up and say something that they knew I had no info on.”

The role of the informants, however, are also reportedly part of Horowitz’s review into potential abuses of FISA. Horowitz’s probe began last year, and Fox News has learned that that investigation is nearing completion. Horowitz’s probe is also focused on the FISA warrants issued and recertified for former Trump campaign aide Carter Page.

BARR REVEALS HE IS REVIEWING 'CONDUCT' OF FBI'S ORIGINAL RUSSIA PROBE

Republicans, for months, have called for a careful review as to whether the FBI violated Page’s constitutional rights, misled the FISA court, or withheld exculpatory information.

The FBI’s ultimately successful October 2016 warrant application to surveil Page, which relied in part on information from British ex-spy Christopher Steele, who compiled the now-infamous anti-Trump dossier, accused Page of conspiring with Russians. Page was never charged with any wrongdoing.

Republicans have also been looking for answers from U.S. Attorney John Huber, who was appointed by former Attorney General Jeff Sessions to review not only surveillance abuses by the Justice Department and the FBI, but also their handling of the investigation into the Clinton Foundation and other matters. Huber apparently has made little progress, and has spoken to few key witnesses and whistleblowers.

Meanwhile, Barr’s appointment of Durham comes after he testified last month that he believed that “spying did occur” on the Trump campaign in 2016.

“I think spying did occur,” Barr said at a congressional hearing. “The question is whether it was adequately predicated…Spying on a political campaign is a big deal.”

Barr later clarified in the hearing: “I am not saying that improper surveillance occurred; I’m saying that I am concerned about it and looking into it, that’s all.”

But FBI Director Chris Wray during a separate congressional hearing broke with Barr’s sentiment.

BARR ASSEMBLES 'TEAM' TO LOOK INTO ORIGINS OF RUSSIA PROBE

“That’s not the term I would use,” Wray told lawmakers on the Senate Appropriations Committee when asked if FBI agents engage in “spying” when they follow FBI policies and procedures.

“Lots of people have different colloquial phrases,” he continued. “I believe that the FBI is engaged in investigative activity, and part of investigative activity includes surveillance activity of different shapes and sizes, and to me the key question is making sure that it’s done by the book, consistent with our lawful authorities.”

But former Attorney General Jeff Sessions, who resigned in November amid a political clash with the president following his decision in 2017 to recuse himself from oversight of the Russia investigation due to his work with the campaign, later took Barr’s side.

“I think that ‘spying’ is a perfectly good word,” Sessions said during an on-stage interview at a conference in Las Vegas last week.

Fox News' Gregg Re and Adam Shaw contributed to this report.