“They even broke into my safe!”

The former president said in a statement that Mar-a-Lago had been “raided, and occupied by a large group of F.B.I. agents.”

The search, according to two people familiar with the investigation, appeared to be focused on material that Mr. Trump had brought with him to Mar-a-Lago, his private club and residence, after he left the White House. Those boxes contained many pages of classified documents, according to a person familiar with their contents.