Aides to US President Joe Biden have discovered at least one more batch of classified documents in a location separate from a think tank office he used after serving as vice-president, news outlets report.

President Biden aides have been searching for additional classified materials that might be in other locations since a set of classified documents was found in November at the Washington-based think tank, according to a report in NBC News, which first broke the news, and CNN.

The NBC News report on Wednesday said the classification level, number and precise location of the additional documents was not immediately clear. It also said it was not clear when the additional documents were discovered and whether the search for any other classified materials President Biden may have from his time as vice-president is complete.

The White House did not immediately respond to a request for comment from Reuters.

Senator Mark Warner, the intelligence committee’s Democratic chairman, has asked for a briefing on the first President Biden document discovery, he said on Tuesday.

A spokesperson for Senator Marco Rubio, the committee’s Republican vice-chair, said Mr Rubio and Mr Warner had written to Director of National Intelligence Avril Haines, asking for access to the classified documents.

The two senators also requested a damage assessment by the intelligence community and a briefing on the retention of classified documents by both President Biden, a Democrat, and Republican former president Donald Trump.

The reports come two days after a White House lawyer said classified documents from Mr Biden’s vice-presidential days had been discovered in November by the president’s personal lawyers at the Penn Biden Center for Diplomacy and Global Engagement think tank.

President Biden’s lawyers discovered fewer than a dozen classified records inside the office at center, and informed the US National Archives of their discovery, turned over the materials, and said they were co-operating with the Archives and the Justice Department.

The president said on Tuesday he and his team were co-operating fully with a review of what happened.

The Justice Department is separately probing Trump’s handling of highly sensitive classified documents that he retained at his Florida resort after leaving the White House in January 2021.

Mr Trump kept thousands of government records, a few hundred of which were marked as classified, inside his personal residence in Florida for more than a year after departing the White House, and did not return them immediately or willingly despite numerous requests by the National Archives.

When he finally handed over 15 boxes of records in January 2022, the Archives discovered more than 100 were marked as classified. It referred the matter to the Justice Department in the spring.

FBI agents carried out a search on August 8 of Mr Trump’s Mar-a-Lago estate. About 100 documents marked as classified were among thousands of records seized.