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Watch: Biden cooperating with classified document review
President Joe Biden has said he was surprised to learn in November that classified files had been found at his former private office.
"I don't know what's in the documents," he said, indicating his lawyers had advised him not to ask about the contents.
The papers, discovered at the Penn Biden Center in Washington, reportedly contain briefings on foreign countries.
A Republican congressional committee says it will investigate.
The oversight panel "is concerned that President Biden has compromised [intelligence] sources", James Comer, its chairman, said.
The US justice department is also reviewing the matter.
Mr Comer, who represents a Kentucky district, has asked the White House to turn over its documents and communications related to the classified materials.
In its request, which is not a legal summons, it also wants a list of people who had access to the office space, by 24 January.
In Mexico City, where he was attending a summit, Mr Biden told reporters on Tuesday that he was "co-operating fully with the review."
The documents relate to his time as vice-president, his lawyer has said, but their level of classification or why they were there is unclear.
Citing a source familiar with the matter, CNN reports that the 10 classified files include US intelligence memos and briefing materials covering topics including Ukraine, Iran and the United Kingdom.
They were found at a private office he used from 2017 to 2020 as it was being cleared out by one of his lawyers, in a manila folder that was labelled "personal", according to CNN.
A source familiar with the matter has told the BBC's US partner CBS News that the batch did not contain nuclear secrets.
The documents were found on 2 November last year, days before the US midterm elections, in a locked closet
Officials are reportedly investigating whether there are additional classified files in other locations tied to Mr Biden.
Mr Biden's predecessor, Donald Trump, faces his own justice department probe for taking sensitive materials to his Florida estate, Mar-a-Lago, after his presidency.
Republicans, who recently took over the US House of Representatives and have pledged to investigate the Biden administration, have accused the president of hypocrisy.
In September, President Biden appeared on CBS and, when asked for his reaction to the documents recovered at Mar-a-Lago, said it was "totally irresponsible".
There are, however, key differences between Mr Biden and Mr Trump's cases.
Mr Trump's inquiry deals with more than 300 documents with classified markings, including 18 marked top secret.
Federal prosecutors allege that Mr Trump's legal team did not adequately co-operate with the National Archives to properly return the documents, prompting a historic FBI raid of his Mar-a-Lago estate last August.
The White House said Mr Biden's lawyers alerted the National Archives as soon as they recovered the materials and the agency retrieved the materials the next morning.
According to CBS News, the FBI is involved in the inquiry and US Attorney General Merrick Garland has been asked to review the papers.
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Mr Trump has been commenting on the matter on his social media site, Truth Social.
"Why didn't the 'Justice' Department announce the Highly Classified documents found in the Biden Office before the Election?" he posted on Tuesday.
"A V.P. cannot Declassify documents," he said in another post, adding: "A President, me, can Declassify."
Neither the Penn Biden Center nor National Archives immediately commented.
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