The FBI also took Biden's notebooks with notes after finding secret documents in his Delaware home

By Carol E. Lee, Sarah Fitzpatrick and Peter Nicholas -

The FBI took a series of notebooks in which the president, Joe Biden, wrote during his time as vice president during a search carried out last week at one of his houses in Delaware, reported exclusively to NBC News, sister network of Noticias Telemundo , a person familiar with the investigation.

The notebooks were seized because, on some pages, the notes refer to Biden's official business as vice president, including details of diplomatic engagements during the Barack Obama administration, and may detail classified information, said this person who requested anonymity.

They are not marked as such, but some notes may be considered confidential. 

Others could be treated as government property under the Presidential Records Act, as they pertain to official business he served as vice president, the person familiar with the investigation said.

On the pages there are notes by Biden's hand on various topics, both personal and official, the source said.

He wrote details about his family or life unrelated to public office and at other times about some of his experiences or thoughts as vice president, the person explained.

[How the Government has failed to protect its classified documents and what internal secrets it has risked]

The exact number of notebooks has not been detailed, but it is large, said the person familiar with the investigation.

When asked, a spokesman for Bob Bauer, Biden's personal attorney, reiterated the position that the president's legal team has taken on the Justice Department's investigation into the discovery of classified Obama Administration material at Biden's Wilmington residence. (Delaware) and in an office in Washington DC that he used after leaving the vice presidency.

"As noted in the statement released on January 14, consistent with our opinion on the requirements of our cooperation with the DOJ in this matter, we will not comment on reports of this nature," the spokesperson said.

The Justice Department declined to comment.

The FBI also did not respond to a request.

Joe Biden in Springfield, Virginia, this January 26.

Andrew Harnik/AP

Bauer's spokesman declined to answer Friday whether Biden knew the notebooks were in boxes he took with him at the end of the Obama administration, has had access to them since leaving the vice presidency and thought they were his personal property.

In a letter sent this week to former presidents and vice presidents, the National Archives asked to search for any materials related to their tenures “to determine whether the materials, previously assumed to be personal in nature, might inadvertently contain presidential or vice presidential records subject to the (Act of Presidential Registries), whether classified or not”.

The request followed a battle between former President Donald Trump and the Files over his possession of classified documents after leaving the White House, which led the FBI to obtain a search warrant in August to recover them from his Mar-a mansion. -Lake;

the discovery of classified documents from Biden's time as vice president in a private office, as well as other subsequent findings;

and the disclosure by former Vice President Mike Pence that his aides found classified documents at his Indiana home this January.

The possession of classified documents by Trump and Biden is the subject of independent investigations.

Attorney General Merrick Garland has yet to appoint a special counsel to investigate Pence's case.

[The National Archives asks former presidents and former vice presidents to check if they have secret documents]

Biden's possession of the notebooks raises questions about whether he properly followed procedures to preserve presidential records.

He also

, and how they have been handled by other vice presidents and presidents who kept similar notes during his tenure.

Federal law allows presidents and vice presidents to write and, upon leaving office, keep “personal” journals and notes, as long as they have not shared them with anyone during their time in office.

Former President Ronald Reagan kept journals during his eight years in the White House, keeping them in a drawer and only his wife, Nancy, knew they were there, said Douglas Brinkley, the presidential historian who later edited and published them.

Jason R. Baron, former director of litigation for the National Archives, said that when it comes to notebooks with handwritten notes on personal matters mixed with notes on government matters, they would likely

during the vice presidency.

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Baron said this applies whether he left a note to himself about buying a birthday present for his wife, or wrote about meeting with a foreign leader, but if Biden shared the content with his staff while he was vice president, it would be it is official government documentation, he explained.

“Handwritten personal notes from a former president or vice president are considered presidential documents if they were shared or communicated with White House personnel or a federal agency for use in government business,” it said.

“A former president or vice president has the right to remove from the White House personal notes that are not official records that pass into the legal custody of the National Archives at the end of an Administration.”

On January 20, the FBI searched Biden's Wilmington home for more than 12 hours looking for possible records from his eight years as vice president, including potentially classified material.

The next day, Bauer, the president's personal lawyer, reported that investigators took more than documents with classified marks after accessing Biden's "handwritten notes, files, papers, folders, memorabilia, to-do lists, diaries, and reminders." that go back decades.”

[“I take full responsibility”: Mike Pence's first remarks on classified papers]

The Justice Department "took possession of materials it deemed to be within the scope of its investigation

, including six items consisting of documents with classification marks and related materials," Bauer said in a statement.

“The DOJ also took personally handwritten notes from the vice presidential years for further review.”

Revelations that Trump, Biden and Pence possessed classified material after leaving the White House have prompted calls for changes to the departure process for presidents and vice presidents.

Norman Eisen, who worked as a special ethics adviser in the administration of former President Barack Obama, advocated for a

, so that they are not stored with the rest of their belongings.

Eisen posed a hypothetical scenario in which an outgoing president or adviser wanted to pack a medical bill that needed to be paid and had to call the National Archives for an employee to determine if it was a personal or government record.

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On Friday, Pence apologized for having classified documents and said he took full responsibility for it.

Biden declared himself surprised by the discovery of classified documents in his former office in November, stating that there is "nothing" in regards to the federal investigation.

The White House legal counsel's office has said the documents were mistakenly packed in boxes and taken away after Biden left the vice presidency.

A person close to the president affirmed that it is impossible to imagine that he packed the boxes when he left the vice presidency.

That would have been the job of his staff, said this person, who spoke on condition of anonymity.

“He's not boxing anything,” this person said.