The committee said it wants those materials by June 23.

Adam Schiff, the ranking Democrat on the House Intelligence Committee, said his committee is now focusing on verifying Comey’s testimony.

“If there are tapes of the conversations at the White House, we’d like to know,” said Schiff.

“Now is the time for a lot of hard spade work.”

Watch: Trump responds to Comey testimony

Verification of Comey’s claims are seen as an important next step in determining if congressional investigators should start focusing on possible obstruction of justice. The former FBI director’s testimony could also prompt an expansion of the ongoing investigation by special counsel Robert Mueller, said Carole Rendon, former US attorney for the Northern District of Ohio.

Rendon, now in private practice at BakerHostetler, said she expects that, following Comey’s testimony “the investigation will expand to include possible obstruction of justice”.

Comey: ‘Lordy. I hope there are tapes’

Comey’s testimony to the Senate Intelligence Committee Thursday was based on notes he made after nine conversations with Trump.

But after Trump fired Comey in May, the president tweeted: “Comey better hope that there are no ‘tapes’ of our conversations before he starts leaking to the press!” The White House has not confirmed if such tapes exist.

The Senate Judiciary Committee, headed by Republican Senator Chuck Grassley, has requested the tapes. The committee has not yet heard back if any tapes exist, and if so, whether they will be turned over.

Jill Wine-Banks, a former Watergate prosecutor, questioned why Republican-led congressional committees have not issued subpoenas for the tapes. Many past presidents have used tape recording systems, either for future use to recheck conversations or for eventual use by historians.

“They forget that the taping system was there, so they have these conversations totally forgetting that they were recording themselves having them,” she said.

In his testimony and prepared seven-page statement for Thursday’s hearing, Comey said that he’d taken the unusual step of making a written record of his conversations because he thought the president “might lie” about them later. He also said that he took it as a “directive” when Trump asked him, in a room he had cleared of a cabinet member and senior advisers, to “let this go” regarding an investigation of his former national security adviser, Michael Flynn.

Trump and his personal lawyer have strongly denied much of Comey’s claims, with the president disputing that he had asked for loyalty from the FBI director and asked him to lay off the Flynn investigation.

Trump cryptically refused to say whether those private exchanges were taped — a matter at the heart of the conflicting accounts of what passed between them at a time when Comey was leading an FBI investigation into Russia’s interference in the presidential election and its ties to the Trump campaign.

He asserted that nothing in Comey’s testimony to the Senate pointed to collusion with Russia or obstruction of justice.

“Yesterday showed no collusion, no obstruction,” Trump said.

He further denied ever asking Comey for his “loyalty”, contradicting Comey’s detailed sworn testimony about a private dinner the two men had in the White House.

“No I didn’t say that,” Trump stated abruptly, taking questions at a joint press conference with Romanian President Klaus Iohannis in the Rose Garden.

Trump’s aides have dodged questions about whether conversations relevant to the Russia investigation have been recorded, and so did the president, in series of teases.

“Well, I’ll tell you about that maybe sometime in the very near future,” Trump said.

Pressed on the issue, he insisted he wasn’t “hinting anything,” before adding: “Oh you’re going to be very disappointed when you hear the answer, don’t worry.”

Additional reporting by Associated Press and Bloomberg