JERUSALEM (AP) — An Israeli military helicopter crashed on Tuesday during training, killing two pilots, the army said.

According to a military statement, the army lost contact with the Bell AH-1 Cobra helicopter in the middle of the night as the aircraft was en route from a routine training flight back to an air base in southern Israel.

The military said it was investigating the crash, and has grounded all similar helicopters until it can determine the cause of the crash.

The two pilots killed in the crash were reservists, the army said.