WASHINGTON (AP) — The FBI searched President Joe Biden’s vacation home in Rehoboth Beach, Delaware, on Wednesday without turning up any classified documents, the latest turn in an extraordinary series of searches of his and his predecessor’s properties.

Agents did take some handwritten notes and other materials relating to Biden’s time as vice president for review, just as they had when they searched his Wilmington home last month where they also found classified items.

Investigators searched his former office at a Washington think tank that bears his name in November, but it isn’t clear whether they took anything.

The Biden searches, conducted with his blessing, have come as investigators work to determine how classified information from his time as a senator and vice president came to wind up in his home and former office — and whether any mishandling involved criminal intent or was merely a mistake in a city where unauthorised treatment of classified documents is not unheard-of.

Law enforcement searches of property are a routine part of criminal probes, but there is nothing ordinary about the FBI scouring a sitting president’s home, even as Biden and his aides have sought to contrast his actions with those of his predecessor.

Former President Donald Trump is facing a special counsel criminal investigation into his retention of several hundred classified documents and other government records at his Mar-a-Lago estate in Florida — and his resistance to giving them up, which led to an FBI warrant and search to seize them last August.

On Wednesday, Biden’s personal attorney Bob Bauer said FBI agents authorised by the Department of Justice spent three and a half hours searching the president’s beach home and that “no documents with classified markings were found.”

In a statement disclosing the search, Bauer sought to portray Biden and his team as fully transparent and cooperative. He described the search as “planned” and “a further step in a thorough and timely DOJ process we will continue to fully support and facilitate.”

He did not mention Trump by name, but the statement seemed aimed at juxtaposing the Biden investigation with the Trump case, where months of fruitless Justice Department efforts to recover all the classified records taken to the former president’s Florida estate culminated in the August search warrant and removal of nearly three dozen boxes of documents and other items.

Searches of Biden’s former office and Delaware homes, by contrast, have all been done voluntarily and without a warrant. But the fact the FBI did its own search reflected the Justice Department’s determination to retrieve any and all possible classified items rather than rely on assurances that such documents had been located.

Biden has said he was surprised by the initial trove discovered by his lawyers in November when they were cleaning out an office inside the Penn Biden Center.

The latest search follows the FBI’s 13-hour, top-to-bottom check of his Wilmington, Delaware, home, where agents located documents with classified markings from his time as a vice president and senator and also took possession of some of his handwritten notes.

One week earlier, Biden’s personal lawyers revealed that they had found a document bearing classified markings while searching the Wilmington property but said they had not found others during a separate inspection of the Rehoboth Beach home.