Helicopter Crash in Yuma Killed 7 Marines During Training Exercise

Seven U.S. Marines were killed along the Arizona-California border Wednesday evening as the result of two helicopters colliding, and new details have emerged as to what may have caused the accident.

The helicopter crash occurred at around 8 p.m. local time when a Cobra and a Huey helicopter collided mid-air during a training exercise off of the Marine Corps Air Station in Yuma, Ariz. The helicopters collided about one hour before the base was set to close for the evening.

"We fly every single day for the most part and, you know, relatively mishap free so it's … one of those rare and unfortunate occurrences that took place last night," Cpl. Steven Posey of the Marine Aircraft Wing in Miramar told MSNBC on Thursday.

While the helicopter collision was reported yesterday, in the day since the accident new details have emerged regarding the incident.

Two of the Marines were aboard the AH-1W Cobra helicopter, while the remaining five Marines were flying in the UH-1 Huey, according to Marine Capt. Staci Reidinger who spoke to KYMA-TV.

It is unknown what the pilots were doing at the exact time of the collision, but the Marines were conducting a training exercise which entailed having helicopters low on fuel descend to fueling posts set up by ground troops, according to The Associated Press.

Six of the Marines came from the Marine Cops Base at Camp Pendleton, and the last Marine was based out of Yuma. The Yuma base is home to around 4,000 active duty Marines and supports 80 percent of air-to-ground aviation training for Marines.

The crash occurred about two miles west of the Yuma, near the Chocolate Mountains along the California-Arizona border. The terrain in the region models that of the harsh terrain of Afghanistan.

The identities of the Marines have still not been released and are pending formal notification of their family members.