A lawyer for former US president Donald Trump signed a statement in June that said all classified material held in boxes at Trump's Mar-a-Lago residence had been returned to the government, the New York Times reported on Saturday.
The statement was signed after Jay Bratt, a top national security official in the US Department of Justice, visited Trump's South Florida beach club on June 3, the New York Times reported. Bratt met with two Trump lawyers to discuss the handling of classified information during the visit, the newspaper said.
Trump is under federal investigation for possible violations of the Espionage Act, which makes it unlawful to spy for another country or mishandle US defence information, including sharing it with people not authorised to receive it, a search warrant made public on Friday showed.
FBI agents searched Mar-a-Lago this week and removed 11 sets of classified documents including some marked as top secret, according to the Justice Department.
The existence of the Trump attorney statement suggests that Trump and his team may not have fully disclosed information about classified documents in the former president's residence, the Times reported.
Reuters was not able to independently confirm the report. The Justice Department declined to comment.
Taylor Budowich, a Trump spokesman, criticised the FBI search in a statement as an "unprecedented and unnecessary raid" that was part of another "Democrat-fabricated witch hunt."
Budowich did not confirm or deny the New York Times report.
The chairs of the House of Representatives Intelligence Committee and the Committee on Oversight and Reform on Saturday asked the director of national intelligence, Avril Haines, to review what damage may have been done to national security by Trump's having the highly classified documents at Mar-a-Lago.
"Former president Trump's conduct has potentially put our national security at grave risk. This issue demands a full review, in addition to the ongoing law enforcement inquiry," the two committee chairs, both Democrats, said in a three-page letter, which they publicly released.
Representative Carolyn Maloney is chair of the Oversight Committee, and Representative Adam Schiff is chair of the Intelligence Committee.