The FBI launched a probe into whether President Donald Trump was secretly "working on behalf of Russia against American interests" shortly after he fired then-FBI Director James Comey in May 2017, The New York Times reported Friday night.

Counterintelligence investigators were so alarmed by Comey’s abrupt dismissal they felt they had to consider Trump’s actions in the context of national security, the Times reported, citing former law enforcement officials and those familiar with the investigation.

The blockbuster report throws a combustible new element into Washington’s already volatile political atmosphere, in which House Democrats are gearing up to launch an aggressive oversight agenda against Trump’s White House, armed with subpoena power.

The question of Trump’s relationship with Russia had already preoccupied FBI agents in the run-up to the 2016 election, but it took on fresh urgency when Trump fired Comey. In addition to probing whether that move amounted to obstruction of justice, agents set about trying to determine whether Trump was knowingly working for Russia or had somehow unwittingly fallen under Moscow’s influence, the Times reported.

Special counsel Robert Mueller was soon brought on to take over the investigation in the chaotic days following Comey’s surprise dismissal. It remains unclear, however, if Mueller is still pursuing the counterintelligence aspect as part of his ongoing probe.

Rudy Giuliani, Trump’s personal attorney, told the Times Friday that the sheer amount of time since the investigation was launched indicated there was nothing to find.

“The fact that it goes back a year and a half and nothing came of it that showed a breach of national security means they found nothing,” Giuliani told the Times Friday.

The White House offered a more acerbic response after the story ran, calling it “absurd,” and slamming Comey.

“James Comey was fired because he’s a disgraced partisan hack, and his Deputy Andrew McCabe, who was in charge at the time is a known liar fired by the FBI,” the White House statement reads.

The report caps a bewildering week of news about Mueller’s Russia investigation, which included the revelation that Trump’s 2016 campaign chairman Paul Manafort handed polling data to a man alleged to be a Russian intelligence asset. The Russian lawyer who met with top brass of the Trump campaign (after being billed as bringing dirt on Trump’s opponent, Hillary Clinton) was indicted by prosecutors in New York for lying, in another matter, about her link to a Russian government official. And Trump’s former personal lawyer and “fixer,” Michael Cohen, agreed to testify before Congress in an open hearing on Feb. 7, in an event likely to focus on some of Trump’s deepest secrets.