Justice Department sources tell Fox News that Attorney General William Barr is working to quickly release the primary conclusions of Special Counsel Robert Mueller's recently concluded Russia investigation. That information, however, wasn't expected to emerge on Saturday.

For Washington insiders, the waiting game isn't easy. Speculation about the hotly anticipated report's contents has been rampant.

Still, in a show of confidence, President Trump waved and flashed two thumbs up to supporters as he returned to his Florida Mar-a-Lago estate on Saturday.

The president's demeanor signaled the administration's strong belief that Mueller's long-awaited final report contained good news. Among other things, the special counsel is not recommending any further indictments as part of his inquiry, which effectively ended Friday, according to a senior Justice Department official.

Further, Mueller did not charge any Americans with illegally conspiring with Russians on any matter, including election interference -- a foundational reason for the launch of the high-profile Mueller probe nearly two years ago.

Even as Trump remained in Florida, Barr was working "hand in hand" on Saturday with Deputy Attorney General Rod Rosenstein in reviewing the Mueller report at the DOJ, the senior official said.

Fox News is told that Barr may run the conclusions past White House Counsel Pat Cipollone and Emmett Flood, who were in Mar-a-Lago, before they are released -- but that Trump's personal attorneys are unlikely to be notified.

It will likely take longer for the facts supporting the conclusions to come out, Fox News is told, because there may be materials that are either classified, or subject to executive privilege in the factual material.

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Barr notified key congressional leaders in a letter Friday evening that Mueller finished his investigation, adding that a summary of the probe’s findings may be provided to lawmakers as soon as this weekend.

Fox News has also confirmed that House Democrats, meanwhile, began a conference call at approximately 3:10 p.m.E.T. Saturday with “chairs of relevant committees” discussing next steps regarding the Mueller report and messaging. New York Rep. Hakeem Jeffries will host as Caucus Chair, and attendees will include Judiciary Committee Chairman Jerrold Nadler, Oversight Committee Chairman Elijah E. Cummings, and Intelligence Committee Chairman Adam B. Schiff, as well as Committee on Financial Services Chairwoman Maxine Waters.

At the meeting, House Speaker Nancy Pelosi pushed for a public release of the Mueller report, and said she would reject any classified briefing of the report's findings to lawmakers. Any briefing must be unclassified so that members of Congress can talk about it publicly, Pelosi said.

Delaware Democrat Sen. Chris Coons, a member of the Judiciary Committee, told Fox News on Saturday: "It’s the end of the beginning. But it’s not the beginning of the end."

He added: "We’re spending the weekend in anticipation of what Attorney General Barr may share with Congress," and cautioned that Democrats were "concerned executive privilege could be asserted broadly here" to hide the report's key findings.

In a Saturday conference call, Coons also issued a warning for his fellow Democrats, many of whom have pinned astronomical political hopes on Mueller's findings: "Once we get the principal conclusions of the report, I think it's entirely possible that that will be a good day for the president and his core supporters."

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Some advocacy groups have made clear they aren't keen on waiting. A nonprofit organization on Friday night filed the first known Freedom of Information Act (FOIA) lawsuit seeking the immediate and total public disclosure of Mueller's completed report and all related documents, echoing bipartisan calls for transparency following his nearly two-year probe into whether the Trump campaign illegally colluded with Russia.

The Electronic Privacy Information Center (EPIC) wrote in an emergency complaint filed in a Washington, D.C., federal district court that the "public has a right to know the full scope of Russian interference in the 2016 United States presidential election and whether the president of the United States played any role in such interference."

The delivery of the Mueller report, which a DOJ official called "comprehensive," does mean the investigation has concluded without any public charges of a criminal conspiracy between the campaign and Russia or of obstruction by the president.

That's good news for a handful of Trump associates and family members dogged by speculation of possible wrongdoing. They include Donald Trump Jr., who had a role in arranging a Trump Tower meeting at the height of the 2016 election campaign with a Kremlin-linked lawyer, and Trump's son-in-law, Jared Kushner, who was interviewed at least twice by Mueller's prosecutors. Still, some key details remain unanswered, EPIC said, prompting its litigation.

House Democrats, meanwhile, have somewhat downplayed the Mueller probe and suggested that the left-leaning lawmakers themselves might take on the job of trying to prove collusion, not ruling out the possibility of Mueller being asked or subpoenaed to testify before congressional committees.

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“If the Justice Department doesn't release the whole report or tries to keep parts of it secret, we will certainly subpoena the parts of the report and we will reserve the right to call Mueller to testify before the committee or to subpoena him,” House Judiciary Committee Chairman Jerry Nadler, D-N.Y., said in a statement.

While the Mueller probe’s conclusions are not yet known, the investigation already has led to indictments, convictions or guilty pleas for nearly three dozen people and three companies. All told, Mueller charged 34 people, including the president's former campaign chairman, Paul Manafort; his first national security adviser, Michael Flynn; and three Russian companies.

Twenty-five Russians were indicted on charges related to election interference, accused either of hacking Democratic email accounts during the campaign or of orchestrating a social media campaign that spread disinformation on the internet.

Five Trump aides pleaded guilty and agreed to cooperate with Mueller, and a sixth, longtime confidant Roger Stone, is awaiting trial on charges that he lied to Congress and engaged in witness tampering.

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Despite all that prosecutorial activity, though, Americans were not implicated in criminally colluding with Russia to influence the election. In a series of posts on Twitter on Friday, journalist Glenn Greenwald -- who also called for the release of the Mueller report -- repeatedly emphasized that point, and condemned pundits for hyping the Mueller report irresponsibly for nearly two years.

"It's truly fascinating to watch Dems grapple with the fact that Mueller finished his work without indicting a single American for conspiring with Russia over the election: everything from "nobody has read his report!" (irrelevant to that fact) to 'sealed indictments!' (unhinged)." Greenwald wrote.

In another post, he criticized media outlets for promoting the anti-Trump rhetoric of partisan commentators like ex-CIA Director John Brennan -- an Obama appointee whose security clearance was revoked last year because, the Trump administration said, he was using it to lend credence to political attacks.

"You can't blame MSNBC viewers for being confused," Greenwald continued. "They largely kept dissenters from their Trump/Russia spy tale off the air for 2 years. As recently as 2 weeks ago, they had @JohnBrennan strongly suggesting Mueller would indict Trump family members on collusion as his last act. ... Oh gosh - turns out that if you hire ex-CIA Directors to be 'news analysts,' they'll abuse our airwaves to disseminate self-serving disinformation."

He concluded: "How - if you're an MSNBC viewer (or consumer of similar online content) - can you not be angry & disoriented having been fed utter [bulls--t] like this for 2 straight years with basically no dissent allowed? Just listen to what they were telling you to believe & how false it was."

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Meanwhile, House Speaker Nancy Pelosi and Senate Minority Leader Chuck Schumer declared it "imperative" to make the full report public, a call echoed by several Democrats vying to challenge Trump in 2020.

"The American people have a right to the truth," Schumer and Pelosi said in a joint statement.

Democrats also expressed concern that Trump would try to get a "sneak preview" of the findings.

"The White House must not be allowed to interfere in decisions about what parts of those findings or evidence are made public," they said in a joint statement.

It was not clear whether Trump would have early access to Mueller's findings. Spokeswoman Sarah Sanders suggested the White House would not interfere, saying, "We look forward to the process taking its course." But Trump's personal attorney, Rudy Giuliani, told The Associated Press Friday that the legal team would seek to get "an early look" before they were made public.

Giuliani said it was "appropriate" for the White House to be able "to review matters of executive privilege." He said had received no assurances from the Department of Justice on that front. He later softened his stance, saying the decision was "up to DOJ and we are confident it will be handled properly."

The White House did receive a brief heads-up on the report's arrival Friday. Barr's chief of staff called White House Counsel Emmet Flood Friday about 20 minutes before sending the letter went to the Republican and Democratic leaders of the Senate and House Judiciary committees.

Fox News' Ed Henry, Mike Emanuel, Brooke Singman, Chad Pergram, Jake Gibson, and The Associated Press contributed to this report.