The FBI has searched the University of Delaware twice in the past month to see if US President Joe Biden donated any papers that might have been classified.
According to CBS, the BBC’s US partner, investigators took multiple boxes from the campus on two different days.
Thousands of cartons of documents from Mr. Biden’s time in the Senate are kept at his alma school, the university.
A criminal investigation into Donald Trump’s handling of sensitive information is ongoing.
Documents marked classified have been found in recent months at Mr Biden’s home in Delaware and offices that he used in Washington DC. The FBI recovered some of the files during a search of his private residence at Wilmington last month.
Sources familiar with the investigation told CBS that the searches at the University of Delaware were carried out at the end of January and beginning of February.
The material recovered did not appear to have classified markings, but the FBI is now reviewing the files, reports CBS.
As with previous searches, Mr Biden and his team consented, meaning no warrant was needed, according to NBC News.
The college received 1,850 boxes of files from Mr Biden in 2012, however, those files have not been available to the public since then.
Mr Biden’s personal lawyer, the US Department of Justice and the University of Delaware have not yet commented.
A special counsel, Robert Hur, has been appointed by the justice department to lead the investigation into how sensitive documents were handled by Mr Biden.
The home of former US Vice-President Mike Pence was also searched last week, after his aides came forward to say that they had discovered documents marked classified during their own search.
Former President Trump is facing a separate investigation after hundreds of papers with classified markings were found by FBI agents executing a search warrant at his Florida Mar-a-Lago estate last year.
Source: BBC