Former Trump national security adviser Michael Flynn told special counsel Robert Mueller that individuals linked to the Trump administration or Congress had reached out to him multiple times, possibly in an attempt to interfere with Mueller’s investigation.

In a court filing on Thursday, the special counsel’s office detailed Flynn’s efforts to aid the inquiry into Russian interference in the 2016 presidential election. The special counsel noted, not for the first time, that Flynn was deeply helpful during the probe, sitting for 19 interviews and providing “substantial assistance.” But the special counsel also said that Flynn informed Mueller’s team of several efforts by people who may have been trying to influence Flynn’s cooperation, both before and after he pleaded guilty to lying to the FBI in late 2017.

“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 have affected both his willingness to cooperate and the completeness of that cooperation,” the filing reads.

Mueller completed his investigation in March and did not find sufficient evidence to conclude that the president had engaged in a criminal conspiracy. But the special counsel did detail 10 instances where Trump may have obstructed justice, although the special counsel declined to make a determination about that.

Flynn is still waiting to be sentenced on his own charges, which are related to conversations he had with then-Russian Ambassador Sergey Kislyak shortly before Trump took office.

Thursday’s memo also notes that Flynn provided a voicemail to investigators of one of those possible attempts to sway him, which was referenced in the full redacted version of Mueller’s report. A personal attorney for Trump left the message on the phone of Flynn’s lawyer.

“[I]t wouldn’t surprise me if you’ve gone on to make a deal with ... the government,” the voicemail states, according to Mueller’s office. “[I]f ... there’s information that implicates the President, then we’ve got a national security issue, ... so, you know, ... we need some kind of heads up. Um, 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.”

U.S. District Judge Emmet Sullivan on Thursday ordered federal prosecutors to provide transcripts of that voicemail message to the federal trial court in Washington, as well as transcripts of any other conversations Flynn had with Russian officials, NBC reported.