FBI Director James Comey has confirmed that his agency is investigating whether President Donald Trump's campaign aides criminally colluded with Russian interests to help him win during the 2016 election.
At a hearing before the House of Representatives Intelligence Committee Monday, Comey also debunked Trump's explosive claim that former President Barack Obama wiretapped him in the weeks before last year's presidential election.
"I have no information that supports [Trump's] tweets" claiming that Obama eavesdropped on him at his Trump Tower headquarters in New York, Comey said.
WATCH: Comey on Trump's claim Obama had him wiretapped
Despite that statement, White House spokesman Sean Spicer later said Trump will not withdraw his wiretapping allegation. "We've started a hearing, it's still ongoing," Spicer said. "There's a lot of areas that still need to be covered. There's a lot of information that still needs to be discussed."
Comey told the panel that because the counterintelligence investigation of Russian efforts to interfere in the U.S. election is classified, "I cannot say more about what we are doing and whose conduct we are examining." He said congressional leaders have been briefed behind closed doors.
But Comey said he has been authorized by the Justice Department to confirm that the Federal Bureau of Investigation probe "includes investigating the nature of any links between individuals associated with the Trump campaign and the Russian government, and whether there was any coordination between the campaign and Russia's efforts."
WATCH: Comey statement about Russia investigation
Hours earlier, Trump derided any suggestion that his campaign colluded with Russian interests to help him win the White House, saying it was an excuse "made up" by Democrats for losing the election.
In a string of messages on his Twitter account, Trump said James Clapper, the director of national intelligence under Obama, and others "stated that there is no evidence" that he joined with Moscow to help his cause. "This story is FAKE NEWS and everyone knows it!" Trump declared.
Two months into his presidency, Trump said Democrats "made up and pushed the Russian story as an excuse for running a terrible campaign," adding that the campaign of former U.S. Secretary of State Hillary Clinton was presumed to have a "big advantage" in the country's Electoral College that determined the outcome, and still lost.
In other tweets Monday, Trump said "the real story that Congress, the FBI and all others should be looking into is the leaking of Classified information. Must find leaker now!" Trump has often complained about leaks of information that have cast a wide shadow on his performance
The White House last week suggested that Obama may have asked the British intelligence agency to wiretap Trump. But Admiral Michael Rogers, the director of the country's National Security Agency, told the House panel that did not occur and that the U.S. and Britain do not spy on each other under a long-standing agreement between the allies.
WATCH: Rogers on British wiretap allegation
Comey said that Obama could not have unilaterally ordered a wiretap on a U.S. citizen such as Trump and would have had to secure a court order to do so, which did not happen.
For more than two weeks, Trump has refused to back down on his wiretapping allegation, even as a string of officials, including House Speaker Paul Ryan and the top Republican and Democratic lawmakers on both the Senate and House Intelligence Committees, have said there is no evidence to support the president's March 4 claims made in a series of Twitter comments.
Republican Congressman Devin Nunes, the chairman of the House panel, acknowledged at the outset of the hearing that there was no evidence of the Obama wiretap on Trump, which Comey later confirmed under questioning from the committee's top Democrat, Congressman Adam Schiff.
Attorney General Jeff Sessions, who oversees the Justice Department and was a staunch Trump supporter during the presidential campaign, said last week he never gave the president any reason to believe he was wiretapped in the weeks before the November election.
Last week, the leaders of of the Senate Intelligence Committee, Republican Richard Burr and Democrat Mark Warner, said in a joint statement, "Based on the information available to us, we see no indications that Trump Tower was the subject of surveillance by any element of the United States government, either before or after Election Day 2016.”
The wiretapping allegation is part of broader investigations by the FBI and lawmakers into the conclusion by the country's intelligence community that Russia meddled in the election to help Trump defeat Clinton.
U.S. investigators say Russian President Vladimir Putin ordered the hacking into the computers at the Democratic National Committee. The anti-secrecy group WikiLeaks subsequently released thousands of emails from the files of Clinton campaign chief John Podesta in the month before the election, showing embarrassing, behind-the-scenes efforts of Democratic operatives to help Clinton win the party's presidential nomination.
But the Trump administration has rebuffed any contention that its campaign aides colluded with Russian officials in that cyberattack. Nunes, the House Intelligence panel chairman, also said he has not seen signs of collusion.