After classified materials were found at an old office of President Joe Biden's, aides discovered a second batch of classified documents at a location that Biden was known to use after leaving office as vice president, ABC News has learned.
Sources familiar with the matter said the second set of documents contained classified information. They came to light as Biden aides conducted an extensive search of locations where he worked after leaving the Obama administration.
Biden aides were responding to the November discovery of classified documents at the Washington, D.C., office of the University of Pennsylvania's Penn Biden Center, which Biden used after his time as vice president.
MORE: Biden 'surprised' about discovery of classified documents and what he's said beforeThe original November discovery was immediately reported to the National Archives and Records Administration, according to White House officials, sparking a Department of Justice inquiry that became public this week.
It is unclear whether the search by Biden aides to check for other potentially classified government documents has been completed yet.
The White House did not comment on the discovery of a second set of documents.
Sources also told ABC News that the original batch of about 10 documents found in November contains classified vice-presidential briefing papers about foreign countries, some of which were marked top secret.
The revelation of a second set of documents, first reported by NBC News, comes the same day that White House press secretary Karine Jean-Pierre declined to provide additional details about why classified documents were apparently improperly stored at Biden's old office at the Penn Biden Center.
The preliminary DOJ inquiry into the possible mishandling of classified documents is focusing on how the documents got there and whether the president played a role.
The preliminary investigation, involving the FBI and the DOJ, has been ongoing for several weeks and is nearing completion. Attorney General Merrick Garland has been briefed and a preliminary finding is expected to be in his hands in the coming weeks, according to sources familiar with the matter.
Garland will face a decision about whether to launch a full-scale criminal investigation and whether to appoint a special counsel.
Biden told reporters on Tuesday in Mexico, while meeting with North American leaders, that he didn't know what was in the records at the Penn Biden Center office and was "surprised to learn" they were there.