WASHINGTON— The FBI has interviewed Huma Abedin, a close aide to Hillary Clinton, as part of a federal investigation into Clinton’s use of a private email server as secretary of state, a person familiar with the probe said Thursday.

The person insisted on anonymity to discuss an ongoing investigation.

The FBI and Justice Department have been investigating whether sensitive information that flowed through Clinton’s email was mishandled. Abedin was one of Clinton’s closest aides during her tenure as the nation’s top diplomat, serving as deputy chief of staff. The interview of Abedin, part of Clinton’s inner circle, is a possible indication that the investigation might be in its final stages. It was not immediately clear whether other aides have been interviewed, or when or if Clinton herself might be questioned.

“From the start, Hillary Clinton has offered to answer any questions that would help the Justice Department complete its review, and we hope and expect that anyone else who is asked would do the same,” Clinton campaign spokesman Brian Fallon said in a statement. “We are confident the review will conclude that nothing inappropriate took place.”

A Justice Department spokeswoman declined to comment Thursday, and a spokesman for the FBI did not return messages seeking comment.

On Wednesday, a federal judge in Washington said he may order Clinton, the Democratic presidential front-runner, to testify under oath about whether she used a private email server to evade public records disclosures.