Arizona Sen. John McCain said in a statement Wednesday he passed along “sensitive information” late last year to FBI Director James Comey, confirming news reports that he had received documents alleging Russia had compromising information about President-elect Donald Trump.

Here is the full McCain statement:

“Late last year, I received sensitive information that has since been made public. Upon examination of the contents, and unable to make a judgment about their accuracy, I delivered the information to the Director of the FBI. That has been the extent of my contact with the FBI or any other government agency regarding this issue.”

The Guardian newspaper in the U.K., which first reported McCain’s involvement, said the senator “dispatched an emissary overseas to meet the source.” McCain gave the material to Comey in person on Dec. 9, the newspaper reported.

McCain has been Congress’ toughest critic of Russian President Vladimir Putin and has taken it upon himself, despite Trump’s protests, to investigate Russian interference in the presidential election.

The senator’s fraught relationship with Trump has been exacerbated by the reports of Russian involvement in the election.

McCain revoked his endorsement of Trump in October after reports that Trump had made lewd comments about women.

During an October debate with Democratic opponent Ann Kirkpatrick, McCain said he did not trust Trump with his finger on the trigger of America’s nuclear arsenal.

The documents, which had been circulated among several news organizations in recent months, allege that Trump representatives had improper contacts with Russian officials and that Russia had material that would personally embarrass the President-elect.

U.S. intelligence chiefs briefed Trump and President Obama on the information last week.

The full dossier that McCain received has been published by a few news organizations; others have refrained because much of the information is unsubstantiated.

In a tweetstorm Wednesday morning, Trump said:

"Russia has never tried to use leverage over me. I HAVE NOTHING TO DO WITH RUSSIA - NO DEALS, NO LOANS, NO NOTHING!"

A Putin spokesman said Wednesday the news reports on the Trump dossier were a “complete fabrication and utter nonsense.” The spokesman said the Kremlin “does not engage in collecting compromising material.”

Arizona Sen. Jeff Flake told NPR Wednesday that he had read the full 35-page dossier on Trump online but added: “We ought to treat them ... as unverified documents. We’ll see where it goes from here.”