The special counsel Robert Mueller's office has reportedly told defense lawyers it is "tying up loose ends" in the Russia investigation, signaling that the inquiry is coming to a close.

This week, prosecutors are also scheduled to file several new documents in court about some of the most important players in the investigation: the former national security adviser Michael Flynn, the former Trump campaign chairman Paul Manafort, and the former Trump lawyer Michael Cohen.

All three men have pleaded guilty and have been cooperating with prosecutors.

The coming court filings are expected to contain intriguing new details about the nature of the men's cooperation and where the Russia investigation is ultimately headed.

The special counsel Robert Mueller's office has told defense lawyers in recent weeks that it is "tying up loose ends" in the investigation into Russia's interference in the 2016 election and whether members of President Donald Trump's campaign colluded with Moscow, Yahoo News reported Monday.

The news is not entirely unexpected. Last month, CNN reported that the special counsel had begun drafting his final report in the Russia investigation.

And this week, prosecutors are set to file several court documents that could reveal major new details about three key players in the Russia investigation: the former national security adviser Michael Flynn, the former Trump campaign chairman Paul Manafort, and the former Trump lawyer Michael Cohen.

All three men have pleaded guilty and have been cooperating with prosecutors.

Flynn has been working with Mueller's team since last December, after he pleaded guilty to lying to the FBI.

In August, Cohen pleaded guilty as part of a separate investigation by the Manhattan US attorney's office, and he has since given over 70 hours of voluntary interviews to the special counsel. He also pleaded guilty in the Mueller investigation to one count of lying to Congress last week, and his lawyers say he expects to cooperate further.

Manafort pleaded guilty to conspiracy and obstruction in September and struck a plea deal with prosecutors to answer any and all questions they had about the Russia investigation and any other federal criminal inquiries.

Read more: What Manafort's highly unusual move to brief Trump's team on his discussions with Mueller reveals about his strategy

What's in store for Manafort

Drew Angerer/Getty Images

But prosecutors late last month accused Manafort of breaching his plea deal by lying to investigators and committing additional crimes since agreeing to cooperate.

Prosecutors were also said to be furious upon learning that Manafort's team was briefing Trump's lawyers on everything he was being asked about after he agreed to cooperate.

Department of Justice veterans told INSIDER that they had never heard of a cooperator maintaining contact with the potential target of an investigation after striking a deal with prosecutors and that such communications could tank a cooperation agreement.

Mueller's team is due to submit a brief to the court on Friday about its claim that Manafort violated his plea agreement. The special counsel's office told Yahoo News that the Manafort memo "will be public," though some parts may be redacted or submitted under seal to protect the investigation.

But for the most part, prosecutors will spell out in detail the matters they believe the former Trump campaign chairman misled them about, and their public disclosures could shed new light on where the Russia investigation stands.

The national security experts at Lawfare wrote, moreover, that the public might also learn more "in the context of that briefing about the relationship Manafort appears to have maintained, through counsel, with the White House after his plea and cooperation agreement."

What's in store for Cohen

Michael Cohen. Drew Angerer/Getty Images

Cohen's lawyers, meanwhile, submitted a sentencing memo on his behalf last week that contained a slew of bombshells about Trump and his interactions with Cohen last year and before the 2016 election.

Among other things, his lawyers said that when Cohen was breaking campaign finance laws at Trump's direction before the election, Cohen was also keeping Trump "contemporaneously informed" of his actions.

They also said Cohen was "in close and regular contact" with Trump's lawyers and White House staffers while he was drafting false testimony to give to Congress last year about his involvement in the Trump Organization's effort to build a Trump Tower in Moscow during the election.

Cohen's sentencing is scheduled for December 12, and prosecutors are set to submit their own sentencing memo in his case on Friday.

Lawfare said it would be important to "see how they characterize Cohen's cooperation and to what extent they also urge leniency and on what points — if any — they dispute the picture of Cohen's cooperation that Cohen's lawyers have painted."

The new filing in Flynn's case could reveal new details about the Russia investigation

Flynn's sentencing hearing is scheduled for December 18, and prosecutors are due to submit a sentencing memo for him on Tuesday.

It's unclear how much of it will be redacted, but because the nature of his cooperation has been shrouded in mystery since last year, it's likely that any new details that come out of the filing will help inform the public about where the Russia investigation is headed.