Seven U.S. Marines were killed in the midair collision of two U.S. military helicopters along the Arizona-California border , officials said Thursday . Six killed in the crash were based at Camp Pendleton , California , and one was from Yuma , Arizona , the Marine Corps said . The crash occurred during routine training operations Wednesday night around 10:30 p.m . ET , according to Marine Corps Air Station Yuma Base Commander Col. Robert Kuckuk . The collision occurred in the Chocolate Mountains on the California side of the range , near Yuma . The aircraft , an AH-1W Super Cobra attack helicopter and a UH-1Y Huey utility chopper , were part of the 3rd Marine Aircraft Wing and based at Camp Pendleton . According to Gunnery Sgt . Dustin Dunk , a spokesperson for Air Station Yuma , two other helicopters were in the immediate area of the collision . Authorities were investigating . `` We wo n't know exactly what happened until the investigation is complete , and we ca n't make any assumptions right now , '' said 1st Lt. Maureen Dooley , a Marine Corps spokeswoman . While weather did not appear to play a factor , visibility may have been severely limited by nightfall and a significant amount of dust , referred to as a `` brown out , '' created by the helicopters landing and taking off , according to Dunk . The Marines on board were preparing for deployment to Afghanistan , Dooley said . `` We have aircraft going out to Yuma training ranges on a weekly basis , and they go out there primarily because the aircraft mimics what they will see in Afghanistan , '' Dooley said . Authorities did not plan to release the names of the Marines involved until their families were notified . `` This tragedy serves as another stark and sad reminder of the peril our men and women in uniform encounter on a daily basis -- not only abroad , but on our own soil . It also reminds us that , whether in combat or training , no military mission is ever routine , '' Arizona Gov . Jan Brewer said in a statement . `` We must never take for granted nor forget these soldiers ' sacrifice and service to the United States of America . '' Marine Corps Air Station Yuma is home to about 4,000 active duty Marines and sailors . It supports 80 % of the Marine Corps air-to-ground aviation training and covers five square miles in southeastern Yuma . The military has long used the AH-1W and UH-1 Huey for a variety of tasks . The military describes the AH-1W as `` the backbone of the United States Marine Corps ' attack helicopter fleet . '' The UH-1Y is a twin-engine , medium-size helicopter .
It is a ` ` stark and sad reminder '' of the peril Marines face , Arizona governor says . The Marine Corps says the crash occurred during routine training . A UH-1Y helicopter and an AH-1W helicopter crash landed . Afghanistan : Marines onboard were ordered to deploy to Afghanistan .