White House lawyer Richard Sauber uncovered the newest documents on Thursday in a box initially discovered by the president's personal lawyers on Wednesday.

The White House revealed earlier this week that Biden's lawyers had discovered one page with classified markings in a room adjacent to the garage of his Delaware home.

"The President’s personal attorneys discovered one document with a classified marking consisting of one page in a room adjacent to the garage. At that point, the President’s personal attorneys stopped searching the immediate area where the document was found," Sauber said.

He said that he reviewed the box further on Thursday, found five more documents with classification markings and immediately transferred them to Justice Department officials.

"Because I have a security clearance, I went to Wilmington Thursday evening to facilitate providing the document the President’s personal counsel found on Wednesday to the Justice Department," Sauber said. "While I was transferring it to the DOJ officials who accompanied me, five additional pages with classification markings were discovered among the material with it, for a total of six pages. The DOJ officials with me immediately took possession of them."

He added, "The President’s lawyers have acted immediately and voluntarily to provide the Penn Biden documents to the Archives and the Wilmington documents to DOJ."

Attorney General Merrick Garland announced Thursday the appointment of Robert Hur to serve as special counsel to review the classified materials found in Biden's home and in an office he used in Washington. The administration will now refer specific questions to the special counsel's office moving forward, Sauber said Saturday.

The White House said earlier this week that Biden's attorneys found a "small" number of classified documents, from his time as vice president, in a locked closet on Nov. 2 at the Penn Biden Center for Diplomacy and Global Engagement in Washington. One of the documents was marked Top Secret/Sensitive Compartmented Information, the highest level of classification in the U.S. government, NBC News has learned.

NBC News reported Wednesday that Biden aides had discovered an additional batch of classified records — which was confirmed by Garland on Thursday when he announced the special counsel.

"We are confident that a thorough review will show that these documents were inadvertently misplaced, and the President and his lawyers acted promptly upon discovery of this mistake," Sauber said in a previous statement.

Biden has said his team is fully cooperating with DOJ's review and that he hoped he'd be able to speak more on the issue "soon."

The president and his aides have declined to answer questions about the content of the documents. “There is a process here. The Department of Justice is independent. We respect that process," White House press secretary Karine Jean-Pierre said Friday.

Bob Bauer, Biden's personal attorney, said in a statement Saturday that his team has abided by the procedures already in place for handling classified documents. When a document with classified markings is discovered, the search must be suspended and the materials left in the place it was found, he added.

"The President’s personal attorneys have attempted to balance the importance of public transparency where appropriate with the established norms and limitations necessary to protect the investigation’s integrity," Bauer said. "These considerations require avoiding the public release of detail relevant to the investigation while it is ongoing."

In a statement issued after the latest disclosure, House Oversight Committee Chair James Comer, R-K.Y., said Saturday, "Many questions need to be answered but one thing is certain: oversight is coming."

Since the first batch of documents were discovered this week, Biden allies have been arguing this case differs from the ongoing criminal probe over former President Donald Trump's possession of classified records at his Florida home.

Their hope is that voters will see the distinction: Biden returned the documents once they were discovered, while Trump did not fully comply with a subpoena and withheld some, triggering a search warrant executed at Mar-a-Lago in August. Biden seemed to be unaware that classified documents had been removed from his office, while Trump, they argue, asked that the documents be taken from the White House.