Three U.S. service members and a civilian employee were killed Thursday night when a helicopter crashed, the Los Angeles Times reports. "Numerous" other people aboard were injured, according to a statement released by NATO's International Security Assistance Force, which also said that the cause of the crash was currently unknown. The Taliban claim they shot down the chopper, but insurgents regularly claim responsibility whenever Western aircraft crash. Mechanical failure or weather conditions are the much more common cause. The craft, an Air Force CV-22 Osprey used for long-range infiltration and supply, contains sophisticated gear. It is unknown whether NATO has been able to secure the scene of the crash.