WASHINGTON (AP) — President Joe Biden has been interviewed as part of an independent investigation into his handling of classified documents, the White House said late Monday. It’s a possible sign that the investigation is nearing its end.

Special counsel Robert Hur is examining the improper retention of classified documents by Biden from his time as a U.S. senator and as vice president that were found at his Delaware home, as well as at a private office that he used in between his service in the Obama administration and becoming president.

Biden has said he was unaware he had the documents and that “there’s no there there.”

Ian Sams, a spokesperson for the White House counsel’s office, said in a statement that the interview was voluntary and conducted at the White House on Sunday and Monday.

Hur’s office likely asked to interview Biden sometime after Aug. 25.

Asked at that time if he planned to sit for an interview with the special counsel, Biden replied, “There’s no such request and no such interest.”

The interview could signal that the special counsel investigation is nearing its conclusion.

In 2016, then-FBI Director James Comey announced his recommendation against criminal charges for former Secretary of State Hillary Clinton, the Democratic presidential nominee, over her handling of classified information just three days after agents interviewed her at FBI headquarters.

Investigators with Hur’s office have already cast a broad net in the Biden probe, interviewing a wide range of witnesses about their knowledge of the handling of classified documents.

In his statement, Sams reiterated that Biden and the White House were cooperating. He referred any questions to the Justice Department.

“As we have said from the beginning, the President and the White House are cooperating with this investigation, and as it has been appropriate, we have provided relevant updates publicly, being as transparent as we can consistent with protecting and preserving the integrity of the investigation,” Sams said. “We would refer other questions to the Justice Department at this time.”

Attorney General Merrick Garland in January 2023 named Hur, a former U.S. attorney for Maryland, to handle the politically sensitive Justice Department inquiry in an attempt to avoid conflicts of interest.

It is one of three recent Justice Department investigations into the handling of classified documents.

The investigation into Biden is separate from special counsel Jack Smith’s probe into the handling of classified documents by former President Donald Trump after he left the White House. Smith’s team has charged Trump with illegally retaining top secret records at his Mar-a-Lago home in Florida and then obstructing government efforts to get them back. Trump has said he did nothing wrong.

No evidence has emerged to suggest that Biden engaged in comparable conduct or willfully held onto records he wasn’t supposed to have.

Questioned in January about the discovery, Biden told reporters that the documents were immediately turned over to the National Archives and the Justice Department. He said he was cooperating fully with the investigation and was “looking forward to getting this resolved quickly.”

“I think you’re going to find there’s nothing there,” he said. “There’s no there there.”

In June, the Justice Department informed former Vice President Mike Pence’s legal team that it would not pursue criminal charges against him related to the discovery of classified documents at his Indiana home. The news came as Pence finalized plans to launch his campaign for the 2024 Republican presidential nomination.

About a dozen documents with classified markings were discovered at Pence’s home in January after he asked his lawyers to search his vice presidential belongings “out of an abundance of caution” after the Biden discovery. The items had been “inadvertently boxed and transported” to Pence’s home at the end of the last administration, Pence’s lawyer, Greg Jacob, wrote in a letter to the National Archives.

The FBI then discovered an additional document with classified markings at the Indiana house during its own search the following month.

Pence repeatedly had said he was unaware of the documents’ existence, but that “mistakes were made” in his handling of classified material.

It is hardly unprecedented for sitting presidents to be interviewed in criminal investigations.

President George W. Bush sat for a 70-minute interview as part of an investigation into the leak of the identify of a CIA operative. President Bill Clinton in 1998 underwent more than four hours of questioning from independent counsel Kenneth Starr before a federal grand jury.

Special counsel Robert Mueller’s team negotiated with lawyers for then-President Donald Trump for an interview but Trump never sat for one. His lawyers instead submitted answers to written questions.