The FBI recovered more than 20 boxes of items – some labelled top secret – during a search of Donald Trump’s Florida mansion, court records show.
Details from a warrant that has now been unsealed, show some items related to defence information.
The warrant said the probe involves alleged violations of the Espionage Act.
A binder of photos and a handwritten note are among the items seized, along with a potential presidential record.
Among the 20 boxes removed were 11 sets of classified documents.
One set was marked as “various classified/TS/SCI documents” referring to top secret and sensitive information.
The FBI searched Mr Trump’s Mar-a-Lago estate in Florida earlier this week, with the former president claiming his home was “raided” and “under siege” and that agents broke open a safe.
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The warrant described the property as “a mansion with approximately 58 bedrooms, 33 bathrooms, on a 17-acre estate”.
It said officers could search the “45 Office” – a reference to Mr Trump’s status as the 45th American president – “all storage rooms, and all other rooms or areas within the premises used or available to be used by FPOTUS” (Former President of the United States).
Also uncovered, according to the “receipt for property,” was information about the “President of France,” and an executive grant of clemency for former Trump ally Roger Stone.
Stone encouraged Mr Trump to run for office, and his staunch support of the president earned him a commuted sentence for his charge following the Mueller investigation into Russian interference in the 2016 election.
The unsealed warrant allowed for “all physical documents and records constituting evidence, contraband, fruits of crime, or other items illegally possessed” to be removed, including: