The helicopter belonging to the 3rd Marine Aircraft Wing at Camp Pendleton went down at about noon in the northern section of the San Diego County base, said 1st Lt. Maureen Dooley, a spokeswoman at the Marine Corps Air Station Miramar. The section is a remote mountainous area where the Marine Corps conducts takeoffs and landings.
Sgt. Derek Carlson, another Marine Corps spokesman, said he had no immediate details on the victim's identity. He said five others remained hospitalized late Wednesday, but didn't release details about their injuries or say whether any were life-threatening.
At least three of the injured were taken to nearby Scripps Memorial Hospital La Jolla in San Diego, about 30 miles south of the base, hospital spokeswoman Lisa Ohmstede said. She said she also couldn't discuss their injuries and she didn't know what other hospitals took in patients from the crash.
Wednesday was sunny and hot in the county so it was unclear if weather played a role. Dooley said there will be an investigation into the cause of the incident.
The UH-1Y helicopter, known as a Yankee Huey is a modernized variant of the decades-old UH-1 design by Bell Helicopter. Among survivability features on the UH-1Y are "crashworthy" crew seats and fuel tanks, according to a description of the aircraft on the Bell Helicopter website. The UH-1Y is described as a medium helicopter with two engines and one four-bladed main rotor.
Associated Press writers Julie Watson in San Diego and Sue Manning in Los Angeles contributed to this report.