Story highlights Hillary Clinton adviser Huma Abedin has spoken to federal investigators as the FBI probes into Clinton's private email

In recent weeks, multiple aides have been interviewed -- some more than once, officials said

(CNN) Some of Hillary Clinton's closest aides, including her longtime adviser Huma Abedin, have provided interviews to federal investigators, as the FBI probe into the security of her private email server nears completion, U.S. officials briefed on the investigation tell CNN. The investigation is still ongoing, but so far investigators haven't found evidence to prove that Clinton willfully violated the law the U.S. officials say.

In recent weeks, multiple aides have been interviewed -- some more than once, the officials said. A date for an FBI interview of Clinton has not been set, these officials said, but is expected in the coming weeks. Abedin has cooperated with the probe, the officials said. Lawyers for Abedin declined to comment. The officials say the interviews of Clinton and her aides would be a routine part of an investigation like this.

The Clinton campaign said Thursday that they've cooperated with the Justice Department review since the beginning.

"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. We are confident the review will conclude that nothing inappropriate took place," Clinton's press secretary Brian Fallon said in a statement.

The probe remains focused on the security of the server and the handling of classified information and hasn't expanded to other matters, the officials said. Spokesmen for the FBI and Justice Department declined to comment. David Kendall, an attorney for Clinton, had no comment.

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