Washington(CNN) Then-FBI Director James Comey knew that a critical piece of information relating to the investigation into Hillary Clinton's email was fake -- created by Russian intelligence -- but he feared that if it became public it would undermine the probe and the Justice Department itself, according to multiple officials with knowledge of the process.

As a result, Comey acted unilaterally last summer to publicly declare the investigation over -- without consulting then-Attorney General Loretta Lynch -- while at the same time stating that Clinton had been "extremely careless" in her handling of classified information. His press conference caused a firestorm of controversy and drew criticism from both Democrats and Republicans.

Comey's actions based on what he knew was Russian disinformation offer a stark example of the way Russian interference impacted the decisions of the highest-level US officials during the 2016 campaign.

The Washington Post reported Wednesday that this Russian intelligence was unreliable. US officials now tell CNN that Comey and FBI officials actually knew early on that this intelligence was indeed false.

In fact, acting FBI Director Andrew McCabe went to Capitol Hill Thursday to push back on the notion that the FBI was duped, according to a source familiar with a meeting McCabe had with members of the Senate intelligence committee.

The Russian intelligence at issue purported to show that then-Attorney General Lynch had been compromised in the Clinton investigation. The intelligence described emails between then-Democratic National Committee Chair Debbie Wasserman Schultz and a political operative suggesting that Lynch would make the FBI investigation of Clinton go away.

In classified sessions with members of Congress several months ago, Comey described those emails in the Russian claim and expressed his concern that this Russian information could "drop" and that would undermine the Clinton investigation and the Justice Department in general, according to one government official.

Still, Comey did not let on to lawmakers that there were doubts about the veracity of the intelligence, according to sources familiar with the briefings. It is unclear why Comey was not more forthcoming in a classified setting.

Sources close to Comey tell CNN he felt that it didn't matter if the information was accurate, because his big fear was that if the Russians released the information publicly, there would be no way for law enforcement and intelligence officials to discredit it without burning intelligence sources and methods. There were other factors behind Comey's decision, sources say.

In at least one classified session, Comey cited that intelligence as the primary reason he took the unusual step of publicly announcing the end of the Clinton email probe.

In that briefing, Comey did not even mention the other reason he gave in public testimony for acting independently of the Justice Department -- that Lynch was compromised because Bill Clinton boarded her plane and spoke to her during the investigation, these sources told CNN.

Multiple US officials tell CNN that to this day Russia is trying to spread false information in the US -- through elected officials and American intelligence and law enforcement operatives -- in order to cloud and confuse ongoing investigations.

UPDATE AND CLARIFICATION: This story has been updated to reflect that there were additional factors behind Comey's decision and to clarify the description of the political operative.