The U.S. Air Force has opened up an investigation after one of its jets accidentally fired a rocket into the Arizona desert. The alarming incident happened Thursday morning when an A-10C Thunderbolt II, better known as the Warthog, “unintentionally released a single M-156 rocket” while carrying out a routine training mission. The Air Force said the M-156 missile—which fires phosphorus smoke to help mark targets and start fires—hit desert wash about 60 miles northeast of Tucson. The area is uninhabited and no injuries or damage have been reported.