The National Archives received 150 or so classified documents in January, a sizable quantity that made authorities there worry that Trump could have hidden more sensitive information behind the walls of the club.
Before they were given over, Trump is said to have personally gone through those crates before the end of last year.
Later, in June, representatives from the Justice Department visited the Florida residence with a subpoena seeking any new secret information.
But after looking over surveillance footage and learning details from conversations with Trump's advisors, they came to the conclusion that there were still more papers that hadn't been disclosed.
The Times said that efforts to return the records to the federal government were made by former White House staffers, but Trump objected, referring to the boxes as "mine."
On August 8, the FBI entered Mar-a-Lago with a search warrant in hand and removed 11 additional sets of sensitive documents. Shortly later, a federal judge declassified the warrant, revealing that Trump was being looked into for potential Espionage Act offenses.