At least one lawyer for former President Donald J. Trump signed a written statement in June asserting that all material marked as classified and held in boxes in a storage area at Mr. Trump’s Mar-a-Lago residence and club had been returned to the government, four people with knowledge of the document said.
The written declaration was made after a visit on June 3 to Mar-a-Lago by Jay I. Bratt, the top counterintelligence official in the…