Shortly after President Donald Trump fired FBI Director James Comey in 2017, the bureau opened an investigation into whether Trump was working on behalf of Russia against U.S. interests, it was reported over the weekend.

According to The New York Times, two particular moments after Comey’s dismissal in May 2017 in which Trump linked the director’s firing to the Russia inquiry sparked the counterintelligence aspect of the probe. Federal investigators had also started to assess, at that point, whether the president’s dismissal of Comey constituted obstruction of justice.

Special counsel Robert Mueller took over the Russia investigation shortly following Comey’s firing and just days after the FBI began its own inquiry into the matter. Mueller is seeking to determine whether Russia interfered in U.S. politics during the 2016 election, and whether or not Trump’s 2016 campaign colluded with the Kremlin. The special counsel — whose team was recently granted a six-month extension for its Russian meddling probe — also started probing Trump’s tweets last summer for potential obstruction of justice. Trump has repeatedly blasted Mueller’s investigation as a “witch hunt” on Twitter, while falsely accusing the special counsel and the FBI of being biased toward Democrats. The president has also claimed his 2016 opponent Hillary Clinton is the one who colluded with Russia.

On Monday, the Huffington Post reported that Trump surprised White House aides on Saturday night after he called in to Fox News to speak with hose Jeanine Pirro and try to dispel recent reports that he was a Russian agent. However, the president was not as forceful in his denial of working for Russia as his advisers would have wished he had been: in fact, Trump appeared to completely deflect Pirro’s question on the subject.

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“I think it’s the most insulting thing I’ve ever been asked,” Trump told Pirro, a close friend whom he invited onstage with him on the eve of the 2018 midterm elections in November. “I think it’s the most insulting article I’ve ever had written, and if you read the article you’ll see that they found absolutely nothing.”

In an interview on Friday, former New York City Mayor Rudy Giuliani — a member of Trump’s legal team — tried to downplay the significance of the FBI’s inquiry into Trump’s alleged work on behalf of Russia.

“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,” said Giuliani.

Trump has repeatedly expressed fondness for Russian President Vladimir Putinwho in turn has praised the former Apprentice host on many issues.