US President Joe Biden delivering a Christmas speech (AFP 2023 / BRENDAN SMIALOWSKI)

Aides to US President Joe Biden have discovered at least one additional batch of classified documents in another location that was used by him after serving as vice president, US media outlets reported on Wednesday, citing unnamed sources.

NBC News and CNN said Biden aides have been searching for additional classified documents that might be in other locations since a first batch of classified documents was found in November at the Penn Biden Center for Diplomacy and Global Engagement think tank in Washington.

According to NBC News, the classification level, number, and exact location of the additional documents were not immediately clear, adding that it was also not clear when the additional documents were discovered.

This comes a couple of days after the White House confirmed that the US Justice Department is reviewing a batch of potentially classified documents found in the office space of Biden's former institute in Washington.

On Tuesday, Senator Mark Warner, the Intelligence Committee's Democratic chairman, said he requested a briefing on the first batch of the Biden documents. In the same context, a spokesperson for Senator Marco Rubio, the committee's Republican vice chair, said Rubio and Warner had written to Director of National Intelligence Avril Haines, asking for access to the classified documents.

The two senators, in addition to Republican Representative Mike Turner of the House of Representatives Permanent Select Committee on Intelligence, requested a damage assessment by the intelligence community and a briefing on the retention of classified documents by both Biden and former US President Donald Trump, as per Reuters.

Richard Sauber, special counsel to Biden, indicated on Monday that "a small number of documents with classified markings" were discovered when the President's personal attorneys were emptying the offices of the Penn Biden Center, where Biden kept an office after he left the vice presidency in 2017 until shortly before he launched his presidential campaign in 2019.

According to Sauber, the documents were found on November 2, 2022, in a "locked closet" in the office, adding that Biden's attorneys immediately alerted the White House Counsel's office, who in turn notified the National Archives and Records Administration, which took custody of the documents the following day.

"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," Sauber noted.

CBS News, which reported first on the documents, cited two sources with knowledge of the inquiry as saying that roughly 10 classified documents were found.

The findings have drawn comparisons to the FBI's August 2022 raid on Trump's Mar-a-logo residence in Florida, which recovered more than 300 classified documents that were once in the former US President's possession. Trump said he wondered when US authorities would raid Biden's home.