FBI Director James Comey said Monday for the first time that the bureau is conducting a counterintelligence investigation into Russia’s interference in the 2016 U.S. elections, including any ties between the 2016 campaign of now-President Donald Trump and Moscow.

As for Trump’s tweets that President Barack Obama ordered wiretapping of Trump Tower, Comey said, “I have no information that supports those tweets.”

Comey made the announcement in his opening statement of the House Intelligence Committee’s first public hearing as part of its investigation into what U.S. spy agencies have concluded was a Kremlin-directed campaign to undermine American democracy and help Trump win the White House.

“That 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,” Comey said.

Comey said the FBI does not normally confirm the existence of an ongoing investigation, but said in unusual circumstances an exception can be made if it is in the public interest. In the case of the Russia investigation, that threshold has been met, he said.

He cautioned, however, that he is limited in what he can say because the FBI does not want to give foreign adversaries clues as to what the bureau knows, or where the investigation is going. He also said he cannot provide a timeline for when the investigation will conclude.

What You Missed at the Russian Interference Committee Hearing

National Security Agency Director Michael S. Rogers said his agency stands by the intelligence community’s previous assessment of Russia’s interference in the 2016 U.S. election.

Intelligence ranking member Adam B. Schiff said in his opening statement that Moscow “successfully meddled in our democracy, and our intelligence agencies have concluded that they will do so again.”

Intelligence Chairman Devin Nunes said in his written statement before the panel’s hearing on Russian election meddling that he wants to focus on Moscow’s interference and potential ties with U.S. political campaigns. Nunes also wants to know about any improper surveillance of the campaigns, and leaks of classified information.