Two U.S. Army helicopters crashed Monday night at a military base in Washington state, killing four soldiers, U.S. media reported. The accidents occurred in a training area of Joint Base Lewis-McChord near the port city of Tacoma, reports quoted the U.S. Army as saying. There was no immediate information about whether the two-seat OH-58 Kiowa observation helicopters collided or crashed separately. Army officials did not disclose whether the wreckage of the two helicopters was found in close proximity. The victims were not immediately identified. The crash sites were secured late Monday and there was an ongoing investigation into the accidents, officials said.