Two Marine pilots have died in a helicopter crash during a training mission in southwestern Arizona, U.S. Marine Corps officials said Sunday.

The AH-1Z Viper crashed Saturday night while the pilots were conducting a training mission as part of a weapons and tactical instructor course, according to the Marine Corps. The cause of the crash is under investigation.

Capt. Gabriel Adibe, a Marine Corps spokesman, said the helicopter crashed on the vast Marine Corps Air Station Yuma training grounds but no additional information was immediately available.

The names of the pilots who died have not been released pending notification of their families.

The station is located about 2 miles (3.2 kilometers) from Yuma and the 1,300-square-mile (3,367-square-kilometer) training ground is one of the world's largest military installations.

There have been several fatal crashes involving Marine Corps aircraft near Yuma over the years.

In 1996, a Marine electronic-warfare plane went down during a training mission on a gunnery range near the Gila Mountains, about 40 miles (64 kilometers) east of the Yuma station, killing all four people aboard. The crew was from the Marine base at Cherry Point, North Carolina, and was training at Yuma.

Two Marine pilots, a crew chief and a Navy corpsman died in a 2007 crash of a search-and-rescue helicopter near the Colorado River during a training mission. The crew members were attached to a headquarters squadron of Marine Corps Air Station in Yuma.

In 2012, seven Marines were killed when an AH-1W Super Cobra attack helicopter and a UH-1Y Huey utility helicopter collided in midair during a training exercise in a remote area of the Yuma training grounds. The crash site was in the Chocolate Mountains on the California side of the range.