Classified documents found at Mike Pence's Indiana home

Lawyers for former Vice President Mike Pence said a "small number" of classified documents were found at his home in Carmel, Indiana, last week.

Pence's lawyers notified the National Archives and Records Administration of the discovery on Wednesday, according to a letter obtained by CNBC.

The classified documents were discovered on Jan. 16 after Pence had outside counsel with experience handling classified documents search his own home and records "out of an abundance of caution," following the news that classified documents were found at President Joe Biden's home and office, an attorney for Pence told the Archives. The discovery, which was reported earlier by CNN, came after Pence said on several occasions he did not have any classified documents.

Gregory Jacob, an attorney at O'Melveny tasked with handling Pence's records, said in a letter sent Sunday to the National Archives that the Justice Department sent FBI agents to Pence's home at 9:30 p.m. on Thursday to retrieve the documents, which were being stored in a safe, while he was in Washington, D.C., for the March for Life.

"We have not heard from the DOJ since then," Pence spokesperson Devin O'Malley told NBC News.

Read Jacob's letters to the National Archives here:

Congressional leaders were informed of the discovery on Tuesday by Pence's team.

O'Malley told NBC News that all four boxes, "the two in which a small number of [classified] papers appearing to bear classified markings had been found, and two separate boxes containing courtesy copies of Vice Presidential papers" were hand-delivered by Pence's legal team to the Archives on Monday.

U.S. Attorney General Merrick Garland has appointed two separate special counsels to investigate Biden and former President Donald Trump for their handling of classified materials.

The White House disclosed on Jan. 9 that documents were found at the Penn Biden Center in Washington, DC on Nov. 2 by personal attorneys for Biden. The attorneys then notified the National Archives, leading to an investigation by the Justice Department. Additional documents were later found by Biden's attorneys at his home in Wilmington, Delaware, on Dec. 20, prompting a search of the home by FBI agents on Friday.

Trump's Mar-a-Lago home in Palm Beach, Florida, was searched by the FBI in August, after months of discussions between the National Archives, Justice Department and Trump. Officials found 15 boxes containing hundreds of documents marked classified in the raid.

Unlike Biden, who agreed to the search, Trump refused to cooperate and was eventually issued a warrant for the search. Trump has repeatedly insisted that he did nothing wrong in his handling of documents after his presidency and has claimed any classified material was declassified by him before he left office, despite evidence pointing to the contrary.

Trump defended his former vice president in a post on his Truth Social website.

"Mike Pence is an innocent man," Trump wrote. "He never did anything knowingly dishonest in his life. Leave him alone!!!"

Special counsel Robert Hur, a former U.S. attorney for Maryland, was tapped by Garland to investigate Biden's handling of classified material on Jan. 12. Garland appointed Jack Smith, a former federal prosecutor, to look into Trump's handling of classified documents on Nov. 18. Smith is also investigating Trump's involvement in the Jan. 6, 2021 attack on the U.S. Capitol.

The FBI declined to comment and referred to the Justice Department which didn't immediately respond to a request for comment.

White House Press Secretary Karine Jean-Pierre declined to comment on the Pence revelations when asked by reporters about it on Tuesday, citing the ongoing investigations.

"The Department of Justice is independent, and we will not politically interfere," Jean-Pierre said. "We've been very, very clear about that."

Biden told reporters in Mexico City on Jan. 10 he was "surprised" by the discovery of the documents.

In an interview with CBS News on Jan. 10, before the documents were found at his home, Pence said that he was "confident" there were no classified materials in his possession from his White House tenure.

"Our staff reviewed all of the materials in our office and in our residence to ensure that there were no classified materials that left the White House or remained in our possession," Pence said. "I remain confident that that was done in a thorough and careful way. Clearly, in the waning days of the Trump-Pence administration, that process was not properly executed by staff around the president of the United States."

Pence told Fox Business on Jan. 12, before classified documents were found at his own home, the situation was a "very serious matter."

"The handling of classified materials and the nation's secret is a very serious matter and as a former vice president of the United States, I can speak from personal experience about the attention that ought to be paid to those materials when you're in office and after you leave office," he told FOX Business. "And clearly that did not take place in this case."

Republican Sen. Lindsey Graham, S.C., told reporters Tuesday the United States could be over-classifying information. Graham also said he believed the documents crisis was now moving beyond politics.

"What became a political problem for Republicans has now become a national security problem for the country," Graham said at a news conference on Capitol Hill.

— CNBC's Kayla Tausche contributed to this article.