The US justice department is reviewing documents marked classified found in President Joe Biden's former office at a think tank, the White House says.

About 10 of the files were discovered in a locked closet at the Penn Biden Center in Washington in November by Mr Biden's legal team, said his lawyer.

The batch has been handed over to the National Archives.

Mr Biden's predecessor, Donald Trump, is facing a probe for taking classified files to Florida after his presidency.

According to the BBC's US partner CBS News, the FBI is involved in the inquiry into classified documents found at the Penn Biden Center, and US Attorney General Merrick Garland has been asked to review the papers.

Mr Biden's lawyer said they relate to the period when he was vice-president. But it is unclear what the documents relate to, the level of classification involved or why they were there.

A source familiar with the matter told CBS News the batch did not contain nuclear secrets and had been contained in a folder in a box with other unclassified papers.

Richard Sauber, special counsel to President Biden, said in a statement to CBS on Monday that the files were discovered just before the midterm elections by Biden attorneys who were clearing out the office space.

Mr Biden kept an office at the think tank, which is about a mile from the White House, from 2017 to 2020....