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.
Just one note to progressive Swampcultists here: Neither OD nor pb defended OrangeMan for possessing classified documents. We were all over the DOJ for the way it handled the search.
pb is not expecting our libs here to respond to this emerging Biden scandal with the same integrity. A President can declassify any federal document but a Vice President has no such authority.
Who's as anxious as pb to read accounts of fibbies rummaging through Jill's undies drawer.
Who else is thankful that pit bull Jim Jordan is chair of the House Oversight Committee?
Oh, and watch the video. Is Joe a hypocrite or is it, simply, dementia?