Joe Biden has claimed he was surprised classified documents were found in a think-tank office he once used and said he and his team were cooperating with a review into why they were there.
Speaking during a visit to Mexico, Mr Biden reporters that he took the issue of classified documents seriously, and that he did not know what was in them.
“I was briefed about this discovery and surprised to learn that there are any government records that were taken there to that office,” he said, at a joint press conference with the leaders of Mexico and Canada.
“We are cooperating fully with the review, which I hope will be finished soon.”
He said his attorneys “did what they should have done” when they immediately called the National Archives about the discovery at the offices of the Penn Biden Centre in Washington DC.
Mr Biden had an office there after he left the vice presidency in 2017 until shortly before he launched his presidential campaign.
CBS News was the first to report that several classified documents from Mr Biden’s time as vice president were discovered last autumn.
Attorney General Merrick Garland has asked the US attorney in Chicago to investigate the matter.
Special counsel to the president, Richard Sauber said “a small number of documents with classified markings” were discovered as Mr Biden’s personal attorneys were clearing out the offices he had once used.
“Since that discovery, the President’s personal attorneys have cooperated with the Archives and the Department of Justice in a process to ensure that any Obama-Biden Administration records are appropriately in the possession of the Archives,” Mr Sauber said.
Republicans have seized on the matter and accused Mr Biden of hypocrisy after the FBI raided Donald Trump’s home last summer and took away many boxes of classified materials, some marked “top secret”. In all, agents discovered more than 300 documents.
The Department of Justice has appointed a special prosector to look into the materials and whether Mr Trump was authorised to retain them after he left the White House. Many have been returned to the National Archives, even as Mr Trump continues to claim he is the victim of political persecution.
“When is the FBI going to raid the many homes of Joe Biden, perhaps even the White House,” Mr Trump wrote on social media on Monday night.
Last year, Mr Biden called Mr Trump “irresponsible” for retaining the documents.
On Tuesday, congressman James Comer, the new Republican chair of the House Oversight Committee, said he was planning to look into the documents found at Mr Biden’s former office.
The Associated Press said he sent the White House Counsel's office a letter requesting copies of the documents found at the Biden office, communications about the discovery, and a list of those who may have had access to the office where they were found.
He said the committte was “concerned that President Biden has compromised [intelligence] sources”.
“We all know that Mar-a-Lago was raided by the FBI, apparently because Donald Trump had taken some documents that were deemed classified to his residence now [and it] was unprecedented to raid the residence of a former president,” he told CNBC.
“The research that we found said every president and vice-president had mistakenly taken a few documents but they had never been raided. President Biden was quick to condemn former President Trump. He called him irresponsible.”
He added: “And now what we found out yesterday is President Biden did the exact same thing, but we haven't seen any raid of President Biden's former residences.”
Mr Biden was attending a trilateral summit with the leaders of Mexico and Canada.
