Former national security adviser Michael Flynn told investigators that people linked to the Trump administration and Congress reached out to him in an effort to interfere in the Russia probe, according to newly unredacted court papers filed Thursday.

The court filing from special counsel Robert Mueller is believed to mark the first public acknowledgement that a person connected to Capitol Hill was suspected of engaging in an attempt to impede the investigation into Russian election interference.

“The defendant informed the government of multiple instances, both before and after his guilty plea, where either he or his attorneys received communications from persons connected to the Administration or Congress that could’ve affected both his willingness to cooperate and the completeness of that cooperation," says the newly revealed section of a sentencing memo originally filed in December.

Flynn even provided a voicemail recording of one such communication, the court papers say.

Prosecutors did not identify any of the people who reached out to Flynn, but said the special counsel's office was in some instances "unaware of the outreach until being alerted to it by the defendant."

No other details were provided in the filing, but the Mueller report noted that President Donald Trump's personal lawyer left a voicemail message for Flynn in late November 2017 that addressed the possibility of him cooperating with the government.

"[I]t wouldn't surprise me if you've gone on to make a deal with ... the government," the attorney said in the voicemail message, according to Mueller.

[I]f... there's information that implicates the President, then we've got a national security issue [so] ... we need some kind of heads-up. Just for the sake of protecting all our interests if we can .... [R]emember what we've always said about the President and his feelings toward Flynn and, that still remains."

In a separate court filing, Judge Emmet Sullivan ordered federal prosecutors to file a transcript of the voicemail message, as well as transcripts of any other recordings of Flynn including his conversations with Russian officials.

Flynn's lawyer Robert Kelner did not immediately return a request for comment. The White House also did not immediately respond to a request for comment.

Two of Trump's personal lawyers, Rudy Giuliani and Jay Sekulow, said they never spoke with Flynn or his attorney.

Flynn pleaded guilty in December 2017 to a charge of lying to the FBI about his conversations with Russian ambassador Sergey Kislyak in the weeks before Trump took office. He faces up to six months in prison. A judge has yet to set a sentencing date.

Mueller's office had previously told the court that Flynn should receive little to no jail time due to his "substantial assistance" in the special counsel's investigation into Russian election interference.

Mueller wrapped up the probe in March, concluding that there was no proof Trump or a member of his campaign conspired with Russia. But the special counsel declined to make a judgment on whether Trump obstructed justice.

Attorney General William Barr and Deputy Attorney General Rod Rosenstein determined that there was insufficient evidence to pursue the matter further.