WASHINGTON (AP) – U.S. officials say the State Department been unable to 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.

Clinton says she handed over all of her work correspondence from her tenure as secretary of state, but the officials said Thursday that these exchanges with longtime confidant Sidney Blumenthal weren’t among the 55,000 pages she provided from her private email account.

The State Department’s inability to find them among the emails she provided likely will raise new questions about her 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.