Former national security adviser Mike Flynn had reportedly been interviewed by the FBI about his communications with the Russian ambassador just days after President Trump took office.

Former national security adviser Michael Flynn was reportedly interviewed by the FBI about his talks with the Russian ambassador days after President Trump took office. 
And, according to The New York Times, inside sources indicated that, “While it is not clear what he said in his F.B.I. interview, investigators believed that Mr. Flynn was not entirely forthcoming.” 
A few days later, on January 26, the Justice Department informed the White House that Flynn could be susceptible to blackmail attempts due to the discrepancies pertaining to what he discussed with the Russian officials. 
On Monday, Flynn formally resigned, with White House press secretary Sean Spicer telling journalists during a press briefing, “The evolving and eroding level of trust as a result of this situation and a series of other questionable instances is what led the president to ask General Flynn for his resignation.” 
While the Washington Post reports that neither the president nor the White House Counsel’s Office suspects he broke any laws, there could be a felony charge if investigators can prove he deliberately lied to the FBI about the conversations.
In an interview with the Daily Caller, Flynn maintained his innocence and blasted the "steady stream of leaks" being shared with the media.