WASHINGTON — The State Department cannot find in its records all or part of 15 work-related emails from Hillary Rodham Clinton’s private server that were released this week by a House panel investigating the 2012 attack in Benghazi, Libya, officials said Thursday.

The emails all predate the Sept. 11 assault on the U.S. diplomatic facility and include scant words written by Clinton herself, the officials said. They consist of more in a series of would-be intelligence reports passed to her by longtime political confidant Sidney Blumenthal, the officials said.

Nevertheless, the fact that the State Department says it can’t find them among emails she provided surely will raise new questions about Clinton’s use of a personal email account and server while secretary of state and whether she has provided the agency all of her work-related correspondence, as she claims.

“She has turned over 55,000 pages of materials to the State Department, including all emails in her possession from Mr. Blumenthal,” said Nick Merrill, a Clinton campaign spokesman, when asked about the discrepancy.

Clinton is running for the 2016 Democratic presidential nomination.

Clinton’s use of the nongovernment email account while in office was kept hidden from all but a small circle of aides, outside advisers, family members and friends. She says the single account for personal and professional purposes was a matter of convenience, and says all her work emails were included in the 55,000 pages of documents she later handed over to the State Department. Emails of a personal nature were destroyed, she says.

The State Department informed the Select Benghazi Committee on Thursday that they are no longer certain that’s the case, according to officials who spoke on condition of anonymity because they weren’t authorized to speak publicly on the matter. The officials said Julia Frifield, assistant secretary of state for legislative affairs, confirmed that nine emails and parts of six others that the committee made public Monday couldn’t be located in the department’s records.

As for 46 other, previously unreleased Libya-related emails published by the committee, officials said all are in the department’s records. They weren’t handed over to congressional investigators because they had no relevance to events in Benghazi.

and did not correspond to the committee’s request, the officials said.