Wednesday’s revelation is a severe blow to the White House, after a week in which it has issued strenuous claims that Trump himself is not the subject of a criminal investigation. Top administration officials frequently touted Comey’s testimony on June 8 that the president had not been under investigation for colluding with Moscow to damage Hillary Clinton’s presidential bid at the time Trump fired Comey.

But Trump, whose anger at Comey for refusing to declare publicly that the president was not under investigation reportedly contributed to his decision to fire him, has now brought about precisely such a criminal probe by dismissing him. A broad cross-section of the American legal community warned that his actions towards Comey could reach the threshold of obstruction of justice, a federal crime cited in the impeachment efforts against both Richard Nixon and Bill Clinton. (Nixon resigned before the House could vote on articles of impeachment; Clinton was impeached for obstruction but not convicted of it.)

According to the Post, Mueller has reached out to NSA Director Mike Rogers, Director of National Intelligence Dan Coats, and former NSA Deputy Director Richard Ledgett to voluntarily interview them as part of the obstruction inquiry. All three men have agreed, the Post said. It’s unclear whether Mueller made his request before Coats and Rogers testified before the Senate Intelligence Committee last week. At that open hearing, both men declined to answer multiple questions from senators about their interactions with the president. The hearing came one day after the Post reported Trump had asked Coats and Rogers in March to intervene with then-director Comey to halt the Russia investigation.

Mueller has also asked the NSA for any documents about its interactions with the president over the Russia investigation, The New York Times reported Wednesday night. Separately, The Wall Street Journal reported that Mueller has requested to interview Rick Ledgett, the NSA’s recently retired deputy director. Ledgett reportedly wrote a memo documenting a phone call between Admiral Mike Rogers, the NSA’s director, and the president. Trump questioned the intelligence community’s assessment that Russia had interfered with the election, and tried to persuade Rogers to say there was no evidence of collusion between the campaign and Russia, the Journal reported.

Trump could theoretically invoke executive privilege to try to block the release of documents like that memorandum, but would be unlikely to find a sympathetic judge: The U.S. Supreme Court blocked Nixon from using the privilege to withhold evidence in a criminal investigation in U.S. v. Nixon in 1974. The Times also reported Mueller is probing the possibility of money laundering by Trump’s associates, on the theory that any collusion with Russian officials might have involved pay-offs, which would then have needed to be concealed.