WASHINGTON (Reuters) – The Federal Bureau of Investigation on Monday raided the offices and home of U.S. President Donald Trump’s personal lawyer Michael Cohen, law enforcement sources said, in a dramatic new development in a series of probes involving close Trump associates. 

Cohen’s lawyer, Stephen M. Ryan, said that U.S. prosecutors conducted a search that was partly a referral by the Office of Special Counsel, Robert Mueller.

Mueller is investigating whether members of Trump’s 2016 campaign colluded with Russia during the U.S. presidential election. Trump has called the probe a “witch hunt” and denied any collusion.

The raid could increase legal pressure on the president, because it involves the records of his longtime attorney and indicates a second center of investigations in Manhattan, alongside Mueller’s Washington-based probe.

Cohen has been at the center of a controversy over a $130,000 payment he has admitted making shortly before the 2016 election to porn star Stormy Daniels, who has said that she had sex once with Trump in 2006 and was paid to keep quiet about it.

Trump reacted with unusually harsh language to news of the raid.

“It’s a disgraceful situation. It’s a total witch hunt. I’ve been saying it for a long time,” Trump said at the opening of a meeting with military and national security advisers to discuss Syria.

Asked whether he would fire Mueller, Trump said, “Well, I think it’s a disgrace what’s going on. We’ll see what happens.”

Trump cannot fire Mueller directly, but he could order Deputy Attorney General Rod Rosenstein, who oversees the special counsel’s probe, to end it, or Trump could fire Rosenstein if he refuses.

In a Tweet, Senate Democratic leader Chuck Schumer warned Trump against interfering.

“If @realDonaldTrump is thinking of using the FBI raid to fire Special Counsel Mueller or otherwise interfere with the chain of command in the Russia probe, we Democrats have one simple message for him: don’t,” Schumer said.

Under federal regulations, if Mueller comes across information that is not directly related to his Russia-focused investigation, he must confer with Rosenstein. Rosenstein could direct Mueller to either investigate the issue himself or refer it to another law enforcement authority.