The lawyer for former national security adviser Michael Flynn met Monday morning with members of special counsel Robert Mueller’s team, ABC News reports, in the latest sign the two sides may be negotiating a plea deal for the embattled former intelligence officer.

Reports emerged late last week that Flynn had alerted White House lawyers that he would no longer be discussing the ongoing investigation, fueling speculation that he is cooperating with prosecutors or negotiating a plea deal.

Flynn’s lawyer, Robert Kelner, did not immediately respond to a request for comment on Monday. He declined to comment on the nature of the Monday morning meeting to ABC News.

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Speculation has grown for weeks that Mueller may have “flipped” Flynn, convincing him to act as an informant on bigger fish in the special counsel’s investigation into Russian meddling in the U.S. presidential election.

Fueling that speculation is the fact that no charges have been filed against Flynn, despite what experts claim is almost-indisputable evidence of wrongdoing and reports Mueller has gathered enough evidence to indict.

Flynn, who stepped down after a mere 24 days in the administration, is seen as vulnerable for a number of reasons.

According to multiple outlets, he is under investigation for an alleged quid pro quo with the Turkish government, in which Flynn would have been paid millions of dollars in exchange for the extradition of a Muslim cleric living in the U.S.

Federal records show that Flynn did not register $530,000 he was paid during the 2016 campaign for work he did that the Justice Department said principally benefitted Turkey, a potential violation of the Foreign Agents Registration Act.

Potentially compounding his legal troubles, congressional Democrats also allege that Flynn violated federal law by failing to report a 2015 trip to Egypt and Israel on his security clearance form.

Heightening the personal drama, Flynn’s son is also thought to be a focus of the Mueller probe, a development the special counsel that could put more pressure on Flynn.

The termination of the information-sharing arrangement with the White House alone does not prove that Flynn is cooperating with Mueller, nor that a plea agreement has been reached.

Defense lawyers often share information during investigations, but stop if there is a conflict of interest — if one client is cooperating with prosecutors while another is still under investigation, for example.

But some lawyers will withdraw from such agreements as soon as they begin negotiating with prosecutors.

The White House has insisted that Flynn has no incriminating information to offer on Trump and that the break was not unexpected.

“No one should draw the conclusion that this means anything about Gen. Flynn cooperating against the president,” Jay Sekulow, a member of Trump's legal team, told ABC News last week.