Two medical helicopters collided yesterday afternoon near a northern Arizona hospital, killing at least seven people and critically injuring three others.
All three people on one of the helicopters were killed in the Flagstaff collision, including a patient and the pilot, said Ian Gregor, spokesman for the Federal Aviation Administration.
Four others were killed and three critically wounded, Mr Gregor said. It is unsure if those killed and injured were all on the second helicopter or whether some were on the ground.
Captain Mark Johnson, a spokesman for the Flagstaff Fire Department, said the helicopters crashed in a wooded area about a kilometre from Flagstaff Medical Centre. The helicopters spread debris across the scene.
"They're not recognisable as helicopters," he said.
Capt Johnson said two emergency workers with a ground ambulance company suffered minor burns in an explosion on one of the aircraft after the crash. The injuries were not life-threatening, he said.
The crash started a 10-acre brush fire that authorities were able to quickly extinguish.
The cause of the crash is being investigated. Both helicopters were Bell 407 models, according to the FAA. One was operated by Air Methods of Englewood, Colorado, and the other by Classic Helicopters of Woods Cross, Utah.