FBI investigators have found additional classified documents from US President Joe Biden’s residence in Wilmington after conducting a 13-hour search of the home, intensifying the probe into discoveries that could become a political and possible legal liability for him as he prepares to launch a re-election bid in 2024.

Bob Bauer, the President’s personal attorney, said in a statement that during the search on Friday, “Department of Justice took possession of materials it deemed within the scope of its inquiry, including six items consisting of documents with classification markings and surrounding materials, some of which were from the President’s service in the Senate and some of which were from his tenure as vice president.”

"DOJ also took for further review personally handwritten notes from the vice-presidential years," he said.

The total number of classified documents found in the residences and private offices of Biden has now increased to nearly a dozen and a half. All documents, including from his term as vice president from 2009 to 2016, have now been taken into possession of federal agents.

DOJ had full access, says Biden’s lawyer

“DOJ requested that the search not be made public in advance, in accordance with its standard procedures, and we agreed to cooperate,” Bauer said.

Biden is spending time at his Wilmington, Delaware residence this weekend. “DOJ had full access to the President’s home, including personally handwritten notes, files, papers, binders, memorabilia, to-do lists, schedules, and reminders going back decades,” Bauer said.

Last week, US Attorney General Merrick B Garland appointed a special counsel Robert Hur to investigate the discovery of the classified documents at the private offices and residence of the President.

Richard Sauber, Special Counsel to the President, said that Biden directed his personal lawyers to be fully cooperative with the Justice Department as part of its ongoing investigation. That has been the case since a small number of materials were initially discovered at the Penn Biden Center, he said.

The President and his team are working swiftly to ensure the DOJ and the Special Counsel have what they need to conduct a thorough review, he said.

“Neither the President nor the First Lady were present during the search. The President’s lawyers and White House Counsel’s Office will continue to cooperate with the DOJ and the Special Counsel to help ensure this process is conducted swiftly and efficiently,” Sauber said.

Political headache

The federal search of Biden’s home, while voluntary, marks an escalation of the probe into the President’s handling of classified documents and will inevitably draw comparisons to his predecessor, former president Donald Trump -- even if the FBI’s search of Trump’s residence was conducted under different circumstances, CNN said.

Trump also faces a probe over his alleged mishandling of hundreds of classified documents at his Florida Mar-a-Lago residence and his alleged failure to comply with a subpoena.

The lengthy search and subsequent discovery of more documents is a political headache and a possible legal liability for Biden, as he prepares to declare whether he will run for a second term.

Biden, 80, already America's oldest sitting president, in November said he intends to run again for the presidency in 2024.

Biden said he was “surprised” to learn of the discovery of the records. He had branded his predecessor Trump, "irresponsible" for storing classified documents at his Mar-a-Lago estate in Florida.

President Biden told reporters in California on Thursday that he "has no regrets" on the handling of documents marked classified. When asked why the White House didn't disclose the existence of the documents in November before the midterm elections, he told reporters he thinks they're going to find out "there's no there there."

A first batch of classified documents had been found on November 2 at the Penn Biden Center, a think-tank Biden founded in Washington DC. A second batch of records was found on December 20 in the garage at his Wilmington home, while another document was found in a storage space at the house on January 12.

After finding the documents, Biden said his team immediately turned them over to the National Archives and the Justice Department.

Under the Presidential Records Act, White House records are supposed to go to the National Archives once an administration ends, where they can be stored securely.

Republicans slam Biden

The Republican Party was quick to slam Biden after the new discovery.

“This says some of the docs are from his Senate service. Serious Q: how on earth did he do that? I’ve served in the Senate for 10 years. Every single classified doc I’ve read—100%—has been in a secure SCIF (sensitive compartmented information facility) in the basement of the Capitol. What the hell??” Senator Ted Cruz said.

“Even more highly classified documents were found in Biden’s home!! How are they just now discovering these? This is getting out of hand. As Vice President, Biden had NO RIGHT to possess these. This scandal is getting bigger every single day!!” Congressman Ronny Jackson said.

“After all the misleading, downplaying statements made by the WH (White House), it’s time for the FBI to seal the crime scene, bar anyone from the WH, including POTUS (President of the United States) and his lawyers, from entering and conducting the search themselves. No more special treatment,” former White House Press Secretary Ari Fleischer said.

Emboldened by a new majority and armed with subpoena power, House Republicans were already gearing up for a series of investigations into the Biden family’s finances and Biden’s son Hunter.

The discovery of the classified documents opens up a new line of inquiry. “I think Congress has to investigate this,” House Speaker Kevin McCarthy said Thursday.