US media say the Justice Department is reviewing a batch of classified documents from Joe Biden's vice presidency found in his private office at a Washington think tank.
Reports say President Biden's personal attorneys found roughly 10 documents marked classified while clearing out the office last November. The attorneys reportedly handed them over to the National Archives the next day.
No details about the documents have been released. Biden served as vice president under Barack Obama until 2017.
US presidents and vice presidents are required by law to hand over all documents related to their duties to the National Archives when they leave office.
The revelation could expose Biden to tough grilling by the Republicans.
Biden has been criticizing his predecessor Donald Trump for taking classified documents out of the White House to his personal residence in Florida. The FBI have seized the documents and the Justice Department is investigating the case.