Two US officers in charge of launching long-range nuclear missiles are under investigation for possessing illegal drugs, officials have said.

The two officers, assigned to Malmstrom Air Force Base in Montana, were being investigated by the Air Force Office of Special Investigations for illegal drug possession, USAF spokeswoman Ann Stefanek told the AFP news agency.

The investigation is the latest in a number of embarrassing incidents and revelations for the USAF's nuclear team, including internal reviews signalling morale problems among missile units and the sacking of a number of senior officers.

Officials acknowledged last month that a two-star US general in charge of land-based ICBMs was fired after he went on a drunken night out in Russia, where he repeatedly insulted his hosts.

Air Force Major General Michael Carey lost his job in October after an inspector general found he had displayed "inappropriate behavior" during the four-day visit to Russia.

According to the inspector general's report, Carey showed up late for motorcades for meetings with Russian representatives, interrupted tour guides and complained over drinks that his unit "had the worst morale".

Malmstrom is home of the 341st Missile Wing and 150 Minuteman 3 intercontinental ballistic missiles - a third of the US's active land-based arsenal.

Staff at Malmstrom last year failed a safety and security inspection. The officer in charge of the inspection noted "tactical-level errors" in a snap exercise.