The FBI on Monday raided the office of Michael Cohen, who has served as Donald Trump’s personal lawyer for years.
The FBI also raided Cohen's personal residence in New York, according to CBS News.
Federal prosecutors in Manhattan obtained search warrants after receiving a referral from special counsel Robert Mueller, according to the New York Times, which first reported the raid.
Agents reportedly seized documents related to payments to adult film star Stormy Daniels, along with other emails, tax documents and business records.
Daniels, whose legal name is Stephanie Clifford, has claimed she had an affair with Trump but was paid $130,000 to keep quiet.
Daniels told CBS News' "60 Minutes" last month that she had unprotected sex with Trump after meeting him at an event in July 2006. She said she originally accepted the hush money because she was afraid.
Cohen has insisted that he made the payment to Daniels out of his own pocket. He has denied that the Trump Organization or the Trump campaign had any involvement.
The records seized from Cohen's office also included communications between Trump and Cohen, the Times reported.
The federal raid does not appear to be a part of Mueller's investigation into alleged Russian interference in the 2016 presidential election, "but likely resulted from information he had uncovered and gave to prosecutors in New York," the Times explained.
Cohen's lawyer described the search as "completely inappropriate and unnecessary."