WASHINGTON (CBSNewYork/CBS News) — An annex to a classified intelligence report reportedly contains unverified details that Russia has potentially compromising information on President-elect Donald Trump.

As CBS2’s Dick Brennan reported, intelligence officials were back on Capitol Hill Tuesday, this time to field questions about their report that accuses Russia of trying to interfere in the presidential election.

And now, CBS News has learned there’s compelling evidence that suggests that it did.

Several government and intelligence officials told CBS News the information that came from a former British intelligence officer was deemed credible, and the information was given to U.S. intelligence last year.

More From CBS News

U.S. intelligence is in the process of corroborating the details of what the Russians may have, but the officials tell CBS News that the former British investigator and his network is credible. Because this information is so sensitive, the annex was not part of the classified report that was distributed to a wider group of people last week.

Multiple government and intelligence officials told CBS News that Russia gathered the potentially compromising information about President-elect Trump, but chose not to disclose it during the 2016 campaign. Instead, it opted only to release emails aimed at damaging the Hillary Clinton’s campaign.

“If this report were true that Russian intelligence had truly compromising material on the President-elect and that there was some cooperation or collusion between his campaign and the Russians, that would be unprecedented in American history,” said U.S. Sen. Chris Coons (D-Delaware).

President-elect Trump responded to the news Tuesday night, tweeting: “Fake News, a total political witch hunt.”

A source told CBS News the classified report was given to President Barack Obama, Trump himself, and eight top Democrats and Republicans in the U.S. Senate and House of Representatives.

It is unclear whether this was actually discussed with Mr. Trump or just part of the materials presented to him during his briefing last Friday.

Trump seemed to respond to the report on Twitter, dismissing it as “fake news.”

Trump’s attorney Michael Cohen disputed parts of an unverified report published by Buzzfeed, calling it, “a fake news story.” The Buzzfeed document claimed Cohen went to Prague to meet with Russian officials and that he is in a “covert relationship with Russia.”

“There is no truth to any of the statements in the reports,” Cohen said to CBS News. “I’ve never been to Prague. In September, I was taking my son to meet with the USC coach. In July of 2016, I was in Capri with my wife for her birthday. I’ve never been to Russia.”

“There is no truth to any of the statements in the reports,” Cohen said to CBS News. “I’ve never been to Prague. In September, I was taking my son to meet with the USC coach. In July of 2016, I was in Capri with my wife for her birthday. I’ve never been to Russia.”

In a pre-tape with NBC’s “Late Night with Seth Meyers,” Trump advisor Kellyanne Conway said that Mr. Trump says he was not briefed on the latest reports, which she called “unsourced” and “not confirmed.”

“It says the FBI is trying to confirm it – so nothing has been confirmed,” Conway said.

“And, I have to say as an American citizen regardless of your party or if you don’t like politics at all, which are many Americans, we should be concerned that intelligence officials leak to the press and won’t go and tell the president-elect or the President of the United States himself now, Mr. Obama what the information is. They would rather go tell the press,” Conway said.

Trump previously acknowledged Russia’s actions, but emphasized they had absolutely no effect on the outcome of the election.

The Tuesday hearing comes as a group of bipartisan senators introduced legislation intended to hit Russia with sanctions for its cyber activities. The bill would impose visa bans and freeze assets of people who engage in significant activates undermining the cyber security of public or private infrastructure or democratic institutions.