Former acting Attorney General Sally Yates told Congress on Monday that she warned the White House that President Donald Trump’s first national security adviser, retired Lt. Gen. Michael Flynn, had misrepresented his contacts with Russian officials and was potentially susceptible to blackmail.

Testifying under oath, Yates provided her first public account of discussions she had in January with White House Counsel Donald McGahn about Flynn’s communications with Russian officials. Much of Yates account was already known through press reports over the past three months, but she did offer new details of her interactions with administration officials regarding Flynn.

Flynn stepped down as national security adviser in February after misrepresenting to Vice President Mike Pence and other senior administration officials the nature of his contacts with Russians.

Yates, testifying before a Senate Judiciary subcommittee hearing on alleged Russian election meddling, said she contacted McGahn on the morning of Jan. 26 to set up a meeting about an urgent matter. The two met that afternoon at McGahn’s White House office, where Yates, accompanied by a senior official from the Department of Justice’s National Security Division, laid out what the DOJ knew about Flynn’s communications with Russians.

“We began our meeting telling him that there had been press accounts of statements from the vice president and others that related conduct Mr. Flynn had been involved in that we knew not to be the truth,” Yates recounted Monday. “We told him we were concerned the American people had been misled.”

The other problem, she noted, was that the Russians also knew that Flynn’s representations of those conversations were inaccurate.

“That created a compromise situation, where the national security adviser could essentially be blackmailed by the Russians,” she said. “We were giving them all this information so that they could take action.”

McGahn called Yates the following morning to discuss Flynn again. In that second meeting, Yates said, the White House counsel asked about the applicability of certain criminal statutes. He also asked why the Department of Justice would care if one White House official had lied to another.

“We told him it was a whole lot bigger than that,” she said. “To state the obvious, you don’t want your national security adviser compromised with the Russians.”

At that point, the FBI had already interviewed Flynn. McGahn, in his conversation with Yates, asked whether White House action against Flynn would interfere with the FBI’s investigation. Yates said that it would not, since Flynn was already aware of the bureau’s probe.

Yates said McGahn also asked to see the evidence underlying the department’s concerns about Flynn. Yates said she would make the arrangements for him to do that, and said he could view the material on Monday, Jan. 30.

Yates was fired on Jan. 30 after instructing the Justice Department not to defend Trumps’ first travel ban in court.

Flynn remained in his job as the president’s top adviser on national security for 18 days after Yates’ informed the White House of DOJ officials’ concerns.

In February, White House Press Secretary Sean Spicer sought to defend the administration’s decision to keep Flynn on for that period, saying Yates had only given the administration a “heads-up” about Flynn. Yates’ testimony Monday made clear that it was more substantive than that.

The hearing was the subcommittee’s second on Russian interference in the 2016 election. The House and Senate Intelligence committees are conducting separate, parallel investigations into Moscow’s meddling, including potential collusion between Russia and Trump campaign officials. The FBI, meanwhile, is carrying out a counterintelligence investigation into possible links between Trump associates and Russia.

The Russia inquiries have loomed over Trump’s first months in office. The president has argued that the suspicions are little more than an effort to undermine his administration.

On Monday, Trump weighed in on the hearing hours before it started, urging lawmakers to press Yates about what the president claims are leaks of classified information to damage his presidency.

“Ask Sally Yates, under oath, if she knows how classified information got into the newspapers soon after she explained it to W.H. Counsel,” Trump tweeted. He also lashed out at his predecessor, saying Flynn “was given the highest security clearance by the Obama Administration — but the Fake News seldom likes talking about that.”

The Obama administration fired Flynn in 2014 from his position as chief of the Defense Intelligence Agency.