Special Counsel Robert Mueller's Russia probe is wrapping up soon, and a source familiar with the investigation tells Fox News it is "near the end game" -- although there has been no formal notification to President Trump's legal team that Mueller's work is completed.

Exiting Deputy Attorney General Rod Rosenstein, who oversaw the Mueller probe for 18 months until the recent confirmation of AG William Barr, had said privately he intended to remain in his role until the Mueller report was delivered to Congress. On Tuesday, the White House announced that Deputy Secretary of Transportation Jeff Rosen would replace Rosenstein.

Sources close to the investigative process have told Fox News that the high-level shakeup at Justice -- with Barr assembling his new team, and Rosenstein planning to leave by mid-March -- is a sign that the stars are aligning for the probe's conclusion.

The DOJ has not confirmed it is planning an announcement on the inquiry, and neither Mueller's team nor the DOJ responded to Fox News' request for comment.

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Also unclear is whether the final Mueller report will be made public. Barr testified during his confirmation hearings that, as he understands the regulations governing the special counsel, the report will be confidential – and any report that goes to Congress or the public will be authored by the attorney general.

Some Democrats sounded the alarm after Barr's testimony, with Connecticut Democratic Sen. Richard Blumenthal charging that Barr indicated he'd exploit legal "loopholes" to hide Mueller's final report from the public and to resist subpoenas against the White House.

"I will commit to providing as much information as I can, consistent with the regulations," Barr had told Blumenthal when asked if he would ensure that Mueller's full report was publicly released.

Mueller's team is still leading several prosecutions, including against longtime Trump adviser Roger Stone on charges of witness tampering and lying to Congress, and against former national security adviser Michael Flynn, who awaits sentencing on charges he lied to FBI agents during the Russia probe. Flynn is cooperating as part of a separate Foreign Agents Registration Act case regarding lobbying work in Turkey as part of his plea deal.

The flurry of activity comes shortly after Iowa Republican Sen. Chuck Grassley -- who until recently was chairman of the Senate Judiciary Committee -- said he expected Mueller's final Russia report "within a month." Grassley later walked back those comments, saying they were based on unconfirmed news reports and rumors.

The top Republicans on the House and Senate Judiciary Committees, meanwhile, are calling for former FBI Acting Director Andrew McCabe and Rosenstein to testify before their respective panels, following McCabe's explosive claims in an interview last week that senior Justice Department officials had considered removing President Trump using the 25th Amendment.

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According to McCabe, Rosenstein offered to wear a wire to record the president, seemingly confirming reports last year. Rosenstein strongly denied that allegation, calling McCabe's statements "factually incorrect."

The 25th Amendment governs the succession protocol if the president dies, resigns or becomes temporarily or permanently incapacitated. While the amendment has been invoked six times since its ratification in 1967, the specific section of the amendment purportedly discussed by top DOJ officials -- which involves the majority of all Cabinet officers and the vice president agreeing that the president is "unable" to perform his job -- has never been invoked.

Fox News' Catherine Herridge and Jake Gibson contributed to this report.