Hillary Rodham Clinton failed to turn over 15 apparently work-related e-mails from her personal server, despite her claim to have disclosed all such correspondence to the State Department, the agency said Thursday.

The missing e-mails, written while she was secretary of state, were instead found among correspondence her longtime adviser Sidney Blumenthal submitted to a House committee probing the 2012 attacks in Benghazi, Libya.

Clinton submitted 30,000 ­e-mails to the State Department last year, claiming they represented a complete record of her work at the agency.

But a State Department official said that while most of Blumenthal’s e-mails to Clinton matched her disclosure, there were “a limited number of instances — 15 — in which we could not locate all or part of the content.”

“The substance of those 15 e-mails is not relevant to the 2012 attacks in Benghazi,” the official added.