Classified documents were found at former Vice President Mike Pence's home, a representative for Pence wrote to the National Archives in letters this month.
This is the latest in a series of scandals involving classified documents at the homes of elected officials and former elected officials.
Classified documents were found at an office at the Penn Biden Center last year, and Biden voluntarily submitted to an FBI search of his home earlier this month.
The Department of Justice executed a search warrant on President Donald Trump's home last year after a long back-and-forth over what documents he had at his Mar-a-Lago estate.
CNN and Fox News first reported the discovery at Pence's home.
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The widening issue underscores what security analysts told USA TODAY when Biden's documents were discovered: The U.S. system of safeguarding classified presidential documents is in urgent need of improvement, especially during the critical period when one administration hands over the White House keys to another.
Earlier in August, when the Associated Press asked Pence if he took any classified documents to his home, he responded, "No, not to my knowledge."
In November, Pence told ABC News the same, saying "there'd be no reason to have classified documents, particularly if they were in an unprotected area."
The Department of Justice "requested direct possession" of the documents on the evening of Jan. 19, and FBI agents went to Pence's home that night to collect the documents from a safe in Pence's home, according to letters from Pence's lawyer obtained by USA TODAY. The action came a day after Pence's lawyer first wrote a letter to the National Archives requesting assistance in returning the documents.
Pence's lawyer characterized the documents as "a small number of documents bearing classified markings that were inadvertently transported to the personal home of the former vice president at the end of the last administration." He said they were found Jan. 16 and placed in a secure safe.
The Jan. 18 letter said Pence was "unaware of the existence of sensitive or classified documents at his personal residence," and that he "understands the high importance of protecting sensitive and classified information and stands ready and willing to cooperate fully with the National Archives and any appropriate inquiry."
Bradley P. Moss, an attorney who has handled national security cases, tweeted: "For the love of everything that is holy can all of you constitutional officers STOP taking home classified documents?!!"
This is a developing story and will be updated.
Contributing: Josh Meyer, Ken Tran, David Jackson.
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This article originally appeared on USA TODAY: Mike Pence had classified documents at his home: Here's what we know