The FBI raided the Alexandria, Va. home of President Trump's former campaign chairman Paul Manafort last month after obtaining a search warrant for documents.

Manafort was not warned about the bust, which took place before sunrise on July 26.

Among the items sought by investigators were Manafort's tax records, according to a New York Times report.

"FBI agents executed a search warrant at one of Mr. Manafort's residences. Mr. Manafort has consistently cooperated with law enforcement and other serious inquiries and did so on this occasion as well," said Jason Maloni, Manafort's spokesman, in a statement.

Federal agents working with special counsel Robert Mueller's team left Manafort's home with a number of records covering a wide-ranging investigation into possible collusion between Trump's campaign and Russia during last year's election, according to the Washington Post.

The raid came one day after Manafort voluntarily sat down with the Senate Intelligence Committee.

Manafort had previously provided documents to the Senate Judiciary Committee, as well as the House and Senate Intelligence Committees, including notes he took about a June 2016 meeting in Trump Tower with Donald Trump Jr., Jared Kushner and a group of Russian citizens.

Federal officials may have obtained the search warrant by arguing Manafort — a former lobbyist for Ukrainian, Philippine, and other world leaders — was not expected to turn over all relevant information for the grand jury subpoena.

Mueller is becoming a central focus in Mueller's investigation. The special counsel is looking at the former GOP political consultant's private business and personal life.

Todd Shepherd contributed to this report.