From the article

"The documents included materials Manafort had already provided to Congress, said people familiar with the search.

“If the FBI wanted the documents, they could just ask [Manafort] and he would have turned them over,” said one adviser close to the White House.

Josh Stueve, spokesman for Mueller, declined to comment, as did Reginald Brown, an attorney for Manafort.

“Mr. Manafort has consistently cooperated with law enforcement and other serious inquiries and did so on this occasion as well,” said Maloni, the spokesman for Manafort."

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