WASHINGTON—The State Department said Tuesday it has found approximately 30 emails from Democratic presidential candidate Hillary Clinton’s account that could be related to the 2012 attacks on two U.S. government facilities in Benghazi, Libya.

The new documents were found among the roughly 15,000 emails forensically recovered by the Federal Bureau of Investigation from Mrs. Clinton’s personal email server as part of its investigation into whether she or her aides mishandled classified information.

...