An Air Force Reserve helicopter crashed and burned during a night training mission, killing 12 people and leaving the three others aboard missing and presumed dead, authorities said Monday.

At dawn, searchers resumed looking for the three, said Capt. Carlos Roque, spokesman at Davis-Monthan Air Force Base.The CH-3E "Jolly Green Giant" helicopter, with four crew members from the base, went down in an uninhabited area 20 miles from Tucson on Sunday while ferrying 11 active-duty Army personnel stationed at Fort Bragg, N.C., Roque said.

"There was another helicopter in the area but there was no damage to the second helicopter," said Roque. "There was no mid-air collision."

The cause of the crash was under investigation. A witness said he saw what appeared to be flames from the helicopter before it crashed. Another said the copters were flying so low that "you could throw a rock and hit them."

Roque said the choppers were not on a low-level mission and were flying "whatever the prescribed altitude was for that area."

He said the helicopter that crashed was on a routine mission transporting the 11 Army personnel from Fort Huachuca, 79 miles southeast of Tucson, to the Air Force's Gila Bend Gunnery Range, 124 miles northwest of Tucson.