The New York Times reported Monday that Donald Trump kept more than 300 classified documents at his residence in Mar-a-Lago.
According to The Times, the documents include information about the FBI, CIA, and National Security Administration.
More than 150 classified materials were contained in the first group of documents, which were recovered by the National Archives in February.
The second set was given to the Justice Department in June. FBI agents searched the Florida golf and country club and recovered documents that included 11 sets of classified material.
A source who had been briefed on the matter told The Times that the files spanned a variety of topics of national security interest.
Insider's requests for comment from the FBI and representatives for Trump were not responded to.
The investigation was denounced by Trump as an unthinkable violation of his rights.
The search on Mar-a-Lago took place after a federal judge signed off on a warrant, which indicated federal agents were looking for information related to national defense. The warrant relied on evidence that is currently being challenged in court.