The memo pads contain writing related to Biden's official business as vice president, a source told the media

Notebooks that US President Joe Biden kept during his time as vice president were among the items seized by the FBI during a search of his home last week, as part of a probe into his mishandling of classified documents, a person familiar with the investigation told NBC.

Despite not being marked as classified, the notebooks were taken because they contain writing related to Biden's official business within the Obama administration, including details of diplomatic contacts, the broadcaster reported on Saturday.

The notebooks were a mix of records on personal and official topics, the source said, adding that pages with no sensitive data could also be considered state property under the Presidential Records Act, as they relate to the activities of the government.

Biden had a "large" number of these notebooks, the person said, but could not provide the exact figure.

When addressed about the notebooks, a spokesperson for Biden's personal lawyer, Bob Bauer, said that "consistent with our view of the requirements of our cooperation with Department of Justice in this matter, we will not comment on the accuracy of reports of this nature."

The possession of notebooks from his time as vice president "raises questions about whether he appropriately followed procedures for preserving presidential records," as well as "how other vice presidents and presidents who kept similar notebooks while in office have handled theirs," NBC said.

The 13-hour search conducted by the FBI at the president's home in Wilmington, Delaware has led to the discovery of six more documents marked as classified, including some dating back to his days as a senator.

Biden landed in hot water after it was revealed earlier this month that several batches of government papers, some marked 'top secret', from his two terms as vice president between 2009 and 2017 were found at his office at the Penn Biden Center, a think tank, and at his Delaware home, including in the garage, in November and January. A special counsel was appointed to investigate the mishandling of the documents by the 80-year-old president.

READ MORE: US Democrats criticize Biden over classified documents

Speaking about the scandal last week, Biden told journalists that "there's no there there," and that he has "no regrets" about the situation. His comments resulted in backlash even from fellow Democrats, including Senator Joe Manchin, who said it was "unbelievable" and "totally irresponsible" for Biden to expose state secrets to potential theft.

(RT.com)