Former national security adviser Michael Flynn "has assisted with several ongoing investigations,” special counsel Robert Mueller said in a court filing late Tuesday night — a signal that the investigation is far from over.

In addition to assisting with the special counsel’s investigation into any connections between the Russian government, the Trump campaign and the Trump transition team, Flynn has assisted in another criminal investigation, of which details were heavily redacted by Mueller’s team.

Because of the "substantial" cooperation — Flynn interviewed with the special counsel’s team 19 times — Mueller's team is asking for no jail time.

“The defendant deserves credit for accepting responsibility in a timely fashion and substantially assisting the government,” Mueller’s team wrote in the heavily redacted, 13-page, two-part memo authored by prosecutor Brandon Van Grack.

Flynn, 59, briefly served as President Trump’s national security adviser from Jan. 20 to Feb. 13, 2017.

Last December, Flynn pleaded guilty to lying to the FBI about his contacts with Russian Ambassador Sergey Kislyak during the 2016 presidential campaign. That made him the second former Trump aide, after George Papadopoulos, to cut a plea deal with Mueller’s team.

Flynn is one of five Trump aides who have pleaded guilty in the special counsel investigation.

Tuesday’s filing is the first time special counsel prosecutors have detailed the extent of Flynn’s cooperation since his guilty plea, 369 days ago.

Mueller's office said that it can't reveal the details of what it called “substantial assistance” from Flynn because “the investigations in which he has provided assistance are ongoing."

In addition, Flynn provided prosecutors with "firsthand information about the content and context of interactions between the transition team and Russian government officials,” Mueller’s team wrote later in the document — conversations that occurred in the weeks before Trump took office between campaign members and transition team members.

“Additionally, the defendant’s decision to plead guilty and cooperate likely affected the decisions of related firsthand witnesses to be forthcoming with the [special counsel] and cooperate,” prosecutors wrote.

Flynn provided documents and communications, said Mueller’s office, but the nature of those were redacted.

“The defendant also provided useful information concerning” another matter that was heavily redacted by Mueller’s team.

The first series of false statements to the FBI began in January 2017, Mueller’s team said in the Tuesday filing. The second series of false statements was during an interview in March 2017.

As early as November 2016, Flynn began having a series of conversations with Kislyak.

In December 2016, Flynn also attended a meeting with Trump’s son-in-law Jared Kushner and Kislyak to discuss a proposed secret communications channel with the Kremlin.

Flynn also admitted in his guilty plea that he spoke with Kislyak about about sanctions imposed by former President Barack Obama following an intelligence report that said Russian President Vladimir Putin had directed Moscow's efforts to interfere in the 2016 election, as well as other topics.

Flynn denied that he ever had the conversations and told Vice President Mike Pence that he did not discuss sanctions. Pence repeated that incorrect assertion in public, and Trump said in February 2017 that he was asking Flynn to resign because of the misleading statements he made to Pence.

"I asked for his resignation. He respectfully gave it. With all that being said, I think he's a fine man,” Trump said said at February 2017 news conference.

What is not included in either Flynn’s guilty plea or the Mueller memo is whether Trump instructed Flynn to communicate with Kislyak, and why Flynn decided to lie about the communications.

Trump has denied that he directed Flynn to call the ambassador, saying during the February 2017 news conference: “No, I didn’t."

At the time of the guilty plea in December 2017, the president's then-lawyer Ty Cobb said nothing in the plea implicated the president.

"I had to fire General Flynn because he lied to the Vice President and the FBI. He has pled guilty to those lies. It is a shame because his actions during the transition were lawful. There was nothing to hide!" Trump said in a Dec. 2, 2017, tweet.

A notable name missing from the Tuesday memo is that of FBI Director James Comey, who wrote in his own personal notes that in a Feb. 14, 2017 meeting with Trump, the president asked him to end the FBI’s investigation into Flynn.

“I hope you can let this go,” Trump reportedly told Comey about Flynn at the Oval Office meeting — which came the day after Trump had fired his former national security adviser.

Trump has denied saying that to Comey.

Comey will be on Capitol Hill on Friday to testify to testify the House Judiciary and Oversight Committees, his first appearance since his June 2017 testimony to Congress.

Throughout 2018, Mueller’s team said Flynn was not yet ready for sentencing “due to the status” of the investigation. On Sept. 17, Mueller said Flynn was ready to be sentenced.

Flynn will be sentenced by federal judge Emmet Sullivan on Dec. 18 in Washington. Flynn’s lawyers have until Dec. 11 to file their own memo describing their client’s cooperation, and addressing any other factors they think is important in sentencing.

In recommending no jail time for Flynn, the special counsel's team noted his 33 years of military service, including five years of combat duty and briefly heading the Defense Intelligence Agency during the the Obama administration.

“The defendant’s record of military and public service distinguish him from every other person who has been charged as part the SCO’s investigation,” said the memo, before later adding that “senior government leaders should be held to the highest standards.”

Mueller’s team is not done with court filings this week.

On Friday, prosecutors are expected to file a sentencing memo for Michael Cohen, the president’s former attorney who pleaded guilty in New York last week to lying to Congress and has agreed to cooperate with the special counsel.

Another memo is due for former Trump campaign chairman Paul Manafort in Washington on Friday. Manafort was indicted by Mueller in both Washington and Virginia. In August, he was convicted of bank and tax fraud in Virginia and in September in Washington he took a plea deal.

Manafort agreed to cooperate, but Mueller’s team has said he breached his plea agreement and has continued to lie in meetings with prosecutors.