The Air Force is investigating after a jet accidentally fired a rocket into the desert about halfway between Phoenix and Tucson, Arizona, on Thursday.

The Air Force said the jet, an A-10C Thunderbolt II, popularly known as the Warthog, "unintentionally released a single M-156 rocket" at about 10:40 a.m. while on a training mission.

No injuries or damage were immediately reported.

The Air Force said the M-156, which fires white phosphorus smoke to help mark targets and start fires, went down in a desert wash about 60 miles northeast of Tucson in an uninhabited area under the Jackal Military Operations Area, which supports air-to-air and night training missions for Davis-Monthan and Luke Air Force bases.

"This training area is not designated for munitions release," the Air Force said.

The Warthog is assigned to the 354th Fighter Squadron of the 355th Fighter Wing at Davis-Monthan on Tucson.