Mueller's team has started writing its final report: CNN

Special counsel Robert MuellerRobert Swan MuellerSasse: US should applaud choice of Mueller to lead Russia probe MORE's team has started writing its final report after a months-long investigation into possible ties between President TrumpDonald John TrumpPentagon update to missile defense doctrine will explore space-base technologies, lasers to counter threats Giuliani: 'I never said there was no collusion' between the Trump campaign and Russia Former congressmen, RNC members appointed to Trump administration roles MORE's presidential campaign and Russia, multiple sources told CNN on Thursday

Trump began reviewing his answers to Mueller's questions as he prepared to request Attorney General Jeff SessionsJefferson (Jeff) Beauregard SessionsBudowsky: Senate must protect Mueller from Barr, President Trump Feinstein grappling with vote on AG nominee Barr Central American women fleeing domestic violence deserve refugee status MORE's resignation, CNN reported.

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A source familiar with the matter told CNN that they believe the Trump legal team will continue to approach Mueller's questions the same way, despite the shakeup in leadership at the Justice Department. 

Trump agreed to answer written questions from the special counsel, but the two teams have not settled negotiations over a possible in-person interview, according to CNN. Trump's legal team and attorneys representing witnesses in the investigation say Trump's responses to the special counsel could point to the imminent conclusion of Mueller's 18-month probe, the network reported.

The special counsel's office declined to comment to The Hill.

Mueller reportedly was expected to release his findings related to key aspects of his investigation into Russian election interference in 2016 after Tuesday's midterm elections.

Shortly after Sessions's ousting, Trump named Matthew Whitaker as acting attorney general, sparking concerns among Democrats that the president could be seeking to undermine Mueller's probe. 

Whitaker, who has publicly criticized Mueller's probe and defended Trump — including in op-eds to CNN and The Hill — will oversee Mueller's investigation. 

Top Democratic leaders, including House Minority Leader Nancy PelosiNancy Patricia D'Alesandro PelosiOvernight Health Care: Dem chair plans hearing on Medicare for all | Senate GOP talks drug prices with Trump health chief | PhRMA CEO hopeful Trump reverses course on controversial pricing proposal Centrist efforts to convince Trump to end shutdown falter On The Money: Shutdown Day 26 | Pelosi calls on Trump to delay State of the Union | Cites 'security concerns' | DHS chief says they can handle security | Waters lays out agenda | Senate rejects effort to block Trump on Russia sanctions MORE (Calif.), have called on Whitaker to recuse himself from oversight over his public comments criticizing the special counsel

"Given his record of threats to undermine & weaken the Russia investigation, Matthew Whitaker should recuse himself from any involvement in Mueller’s investigation," Pelosi said. "Congress must take immediate action to protect the rule of law and integrity of the investigation. #FollowTheFacts.

Democrats on the House Judiciary Committee on Thursday called for an emergency hearing following Sessions's resignation.

Committee Democrats sent letters to the panel's GOP chairman and Whitaker, pressing them on how the shakeup at the highest levels of the Justice Department will impact Mueller's investigation. 

Whitaker, in an op-ed for The Hill last year, criticized the idea of a special counsel, dismissing the call for an independent counsel as partisan.

"Calls for an independent counsel or commission to investigate allegations that Russia tried to interfere with our elections ring hollow when similar calls for special counsels during the scandals of the Obama administration were dismissed out of hand by the same people making these demands now," Whitaker wrote at the time. 

Olivia Beavers contributed reporting.