The Federal Bureau of Investigation may have seized tapes that President Donald Trump’s personal attorney, Michael Cohen, kept of conversations with associates.

According to the Washington Post, people who have interacted with Cohen were familiar with his practice of using the recorded conversations as leverage. While it is unclear whether Cohen recorded his conversations with Trump, associates said he recorded conversations regarding both business and politics, and one person said Trump knew of the practice.

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During its raid of Cohen’s office, hotel and home, the FBI took his computers and phones.

“If you are looking for evidence, you can’t do any better than people talking on tape,” Nick Akerman, a former Watergate prosecutor told the Post

Trump’s campaign staff believed Cohen may have recorded people secretly. In the state of New York, this is legal, as it is a one-party state and requires that only one person participating in a conversation knows it is being recorded.

The FBI is said to have been looking for documents relating to Cohen’s $130,000 payment for Stormy Daniels’ silence several years ago. Trump quickly denounced the raid, calling it a “witch hunt” and “an attack on our country.”

While the Justice Department has not released its findings, it revealed earlier today that it is investigating Cohen.