The Air Force is investigating about a dozen airmen at a nuclear missile base for alleged use of illegal drugs, in some cases possibly including cocaine, defense officials said Friday. The probe is a fresh blow to a nuclear missile corps that has been under intense scrutiny for a string of lapses in training and personal conduct over the past three years.

The drug investigation at F.E. Warren Air Force Base, home of the 90th Missile Wing, was to be announced Friday by Gen. Robin Rand, the four-star commander of Air Force Global Strike Command. The command is responsible for the entire fleet of Minuteman 3 land-based nuclear missiles; one-third of the Minuteman 3 force is operated by the 90th Missile Wing.