Members of a US Air Force nuclear missile crew face disciplinary action for going to sleep while in possession of an invalidated nuclear launch code component, the air force disclosed.

The breach occured July 12 at Minot Air Force Base in North Dakota, the scene of two other recent high profile lapses involving nuclear weapons or nuclear-related components, according to the spokesman Thursday.

An investigation into the violation of procedures "concluded that no compromise of the classified material occurred," the air force said in a statement.

The nuclear launch code component is a device that enables the missile crew to issue an electronic command to launch a nuclear missile. The codes are changed on a scheduled, recurring basis.

The four member missile crew changed the codes in the underground launch control centre during their watch and had gone "top side" to an above ground missile alert facility with the component containing the old codes to await transportation back to the main base, the air force said. 

While awaiting transportation, they went into a crew rest area with bunks where they fell asleep, a violation of the rules, according to the air force.

"An investigation revealed the codes had remained secured in containers using locks which combos were known only to the crew during the entirety of the incident," the air force said.

"Additionally, access to the MAF (missile alert facility) was continually controlled by air force security forces and the codes had been superseded and were unusable," it said.

The breach was reported by one of the missile crew members.