Two helicopters collided in during a training exercise in near the Arizona's Yuma Training Range Complex Military base, killing seven Marines on Wednesday.

The U.S. Marine Corps made the announcement on Thursday that an AH-1W Super Cobra and a WH-1Y Heuy crashed in midair during training operations in the Chocolate Mountains in southeast California, the Associated Press reports, reported CNN. Authorities are still investigating the crash.

The aircraft, an AH-1W Cobra and an UH-1Y Huey, were conducting routine training operations around 8:00 p.m (local time), said Maj. Carl B. Redding, Jr., said in a statement. Identities of the Marines will be withheld until next of kin have been notified. The incident is currently under investigation.

The Marines were from the 3rd Marine Airwing based at Miramar in Southern California, reported USA Today.

There are approximately 4,000 active duty Marines and sailors stationed at the base.

With access to 2.8 million acres of bombing and aviation training ranges and superb flying weather, MCAS Yuma supports 80% of the Corps' air-to-ground aviation training, said the website My Base Guide.

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