By CHRIS MEGERIAN and WILL WEISSERT

WASHINGTON (AP) — President Donald Trump intensified his assertions — without evidence — that officials using an autopen undermined the actions of his predecessor, Joe Biden, even suggesting Thursday that “essentially whoever used the autopen was president.”

“I happen to think I know” who was using a tool that allows for auto signatures, Trump told reporters in the Oval Office, while saying it was the “biggest scandal” in years.

The Justice Department under Democratic and Republican administrations has recognized the use of an autopen to sign legislation and issue pardons for decades. Trump presented no evidence that Biden was unaware of the actions taken in his name, and the president’s absolute pardon power is enshrined in the U.S. Constitution.

“It’s a very bad thing, very dangerous,” Trump said, arguing that, “Essentially, whoever used the autopen was the president.”

Those comments came a day after Trump directed his administration to investigate Biden’s actions as president, alleging aides masked his predecessor’s “cognitive decline” and casting doubts on the legitimacy of his use of the autopen to sign pardons and other documents. An executive order he signed marked a significant escalation in Trump’s targeting of political adversaries and could lay the groundwork for arguments by the Republican that a range of Biden’s actions as president were invalid.

Biden responded in a statement Wednesday night: “Let me be clear: I made the decisions during my presidency. I made the decisions about the pardons, executive orders, legislation, and proclamations. Any suggestion that I didn’t is ridiculous and false.”

Trump wrote in a memo Wednesday that, “This conspiracy marks one of the most dangerous and concerning scandals in American history.”

The American public, he said, “was purposefully shielded from discovering who wielded the executive power, all while Biden’s signature was deployed across thousands of documents to effect radical policy shifts.”

Trump directed Attorney General Pam Bondi and White House counsel David Warrington to handle the investigation.

Even as Trump doubled down on his accusations, it is unclear how far Trump will push this effort, which would face certain legal challenges. It nonetheless reflects his fixation on Biden, who defeated him in 2020, an election that Trump never conceded and continues to falsely claim was rigged against him. In lobbing allegations against Biden on Thursday, Trump continued to insist that the 2020 election was stolen from him.

Trump frequently suggests that Biden was wrong to use an autopen, a mechanical device that replicates a person’s authentic signature. Although they’ve been used in the White House for decades, Trump claims that Biden’s aides were usurping presidential authority.

Biden issued pardons for his two brothers and his sister shortly before leaving office, hoping to shield them from potential prosecution under Trump, who had promised retribution during last year’s campaign.

Other Biden pardon recipients included members of a congressional committee that investigated the Jan. 6, 2021, riot at the U.S. Capitol.

Trump often suggests that his political opponents should be investigated, and he has directed the Justice Department to look into people who have angered him over the years. They include Chris Krebs, a former cybersecurity official who disputed Trump’s claims of a stolen election in 2020, and Miles Taylor, a former Department of Homeland Security official who wrote an anonymous op-ed sharply critical of the president in 2018.

Meanwhile, House Oversight Chairman James Comer of Kentucky, a Republican, requested transcribed interviews with five Biden aides, alleging they had participated in a “cover-up” that amounted to “one of the greatest scandals in our nation’s history.”

“These five former senior advisors were eyewitnesses to President Biden’s condition and operations within the Biden White House,” Comer said in a statement. “They must appear before the House Oversight Committee and provide truthful answers about President Biden’s cognitive state and who was calling the shots.”

Interviews were requested with White House senior advisers Mike Donilon and Anita Dunn, former White House chief of staff Ron Klain, former deputy chief of staff Bruce Reed and Steve Ricchetti, a former counselor to the president.

Comer reiterated his call for Biden’s physician, Kevin O’Connor, and former senior White House aides Annie Tomasini, Anthony Bernal, Ashley Williams and Neera Tanden to appear before the committee. He warned subpoenas would be issued this week if they refuse to schedule voluntary interviews.

“I think that people will start coming in the next two weeks,” Comer told reporters. He added that the committee would release a report with its findings, “and we’ll release the transcribed interviews, so it’ll be very transparent.”

Rep. Brandon Gill, a freshman Republican from Texas, said “the American people didn’t elect a bureaucracy to run the country,” said “I think that the American people deserve to know the truth and they want to know the truth of what happened.”

Democrats have dismissed the accusations as a distraction.

“Chairman Comer had his big shot in the last Congress to impeach Joe Biden and it was, of course, a spectacular flop,” said Rep. Jamie Raskin, the Maryland Democrat who served as the ranking member on the oversight committee in the previous Congress. “And now he’s just living off of a spent dream. It’s over. And he should give up the whole thing.”