WASHINGTON — The Air Force said on Wednesday that 34 officers responsible for launching the nation’s nuclear missiles had been suspended, and their security clearances revoked, for cheating on monthly proficiency tests that assess their knowledge of how to operate the warheads.

At a news conference, Deborah Lee James, the secretary of the Air Force, said the officers, at Malmstrom Air Force Base in Montana, either knew about or took part in texting answers to the routine monthly tests.

Eleven Air Force officers — including two accused in the Malmstrom cheating scandal, as well as one other nuclear missile officer — have also been the focus of suspicion in an illegal drugs investigation, defense officials said.

Although the Air Force has been plagued in recent years by scandals, the current revelations are particularly alarming because they involve America’s nuclear arsenal, where errors could be catastrophic.