WASHINGTON (Reuters) – A U.S. House of Representatives committee will look into a news media report that the FBI investigated whether President Donald Trump has been working on behalf of Russia, against U.S. interests, the panel’s Democratic chairman said on Saturday.

The New York Times reported that the probe began in the days after Trump fired James Comey as FBI director in May 2017 and said the agency’s counterintelligence investigators had to consider whether Trump’s actions constituted a possible threat to national security.

The White House rejected the Times article as “absurd” late on Friday, while Trump himself lashed out at Comey and the FBI in half a dozen tweets on Saturday.

House Judiciary Committee Chairman Jerrold Nadler said his panel “will take steps to better understand both the president’s actions and the FBI’s response to that behavior” in coming weeks. He also said lawmakers would seek to protect investigators from the president’s “increasingly unhinged attacks.”

“There is no reason to doubt the seriousness or professionalism of the FBI, as the president did in reaction to this story,” Nadler, a New York Democrat, said in a statement.

“We have learned from this reporting that, even in the earliest days of the Trump administration, the president’s behavior was so erratic and so concerning that the FBI felt compelled to do the unprecedented — open a counterintelligence investigation into a sitting president,” Nadler said.

The Times said FBI officials became suspicious of Trump’s ties to Russia during the 2016 presidential campaign but held off on opening an investigation until Trump tied his dismissal of Comey to a probe into allegations of election meddling by Russia. The FBI also considered whether the Republican president’s firing of Comey amounted to obstruction of justice.

U.S. Special Counsel Robert Mueller took over the investigation into Trump days after the FBI opened it, as he examined allegations of Russian election interference, the Times reported. Russia denies it sought to influence the election.

Trump responded on Saturday by lashing out at the Times and former FBI leaders, and criticized the agency’s earlier probe of Democrat Hillary Clinton, his rival in the 2016 election.

“Wow, just learned in the Failing New York Times that the corrupt former leaders of the FBI, almost all fired or forced to leave the agency for some very bad reasons, opened up an investigation on me, for no reason & with no proof, after I fired Lyin’ James Comey, a total sleaze!,” Trump tweeted.

Comey took to Twitter later on Saturday, offering a quote he attributed to former President Franklin Delano Roosevelt: “I ask you to judge me by the enemies I have made.”