"I was briefed about this discovery and surprised to learn that there were any government records that were taken there to that office, but I don't know what's in the documents," Biden said during a joint conference with his Mexican and Canadian counterparts on Tuesday.
"My lawyers have not suggested I ask what documents they were. I've turned over the boxes. they've turned over the boxes to the [National] Archives and we're cooperating fully, cooperating fully with the review and which I hope will be finished soon."
The US president underscored that he "takes classified documents and classified information seriously."
The White House confirmed on Monday that a "small number" of documents with classified markings had been found at the Penn Biden Center inside a locked closet on November 2, 2022, in Washington, DC. The documents dated back to the commander-in-chief's days as vice president under the Obama administration.
White House Special Counsel Richard Sauber has explained that the office space was used "periodically" by Biden during from mid-2017 to the beginning of his 2020 campaign. The National Archives were said to have been alerted to the findings on the same day of discovery, with the agency collecting the files the following day.
"The documents were not the subject of any previous request or inquiry by the Archives," Sauber said in a statement.
Although details of the information contained in the files remain scarce, US media reported on Tuesday that the documents contained information on Ukraine, Iran and the UK. However, officials have yet to comment on the matter.
The development was first reported by CBS News, and has since prompted the US Attorney General's Office to undertake an initial facts-based investigation. It's expected that Attorney General Merrick Garland will soon decide on whether or not to appoint a special counsel on the matter.
The latest also comes amid an ongoing back and forth between the US government and former US President Donald Trump, who saw his Florida estate raided by FBI agents after it was determined to house boxes of classified files. Trump, who has refused to cooperate in the ongoing probe, weighed in on the Biden fiasco, asking whether a raid would be imminent.