A preliminary investigation into last week's fatal crash of a U.S. Army medevac helicopter indicates the Black Hawk (search) was shot down, a U.S. military official said Saturday.

Iraqi witnesses reported seeing a projectile strike the second of two medevac helicopters on Thursday as they flew south of the city of Fallujah (search), a major center of resistance to the U.S. occupation.

Brig. Gen. Mark Kimmitt told reporters that the cause of the crash, in which nine soldiers were killed, has not been completed.

"But the preliminary reports indicate that the medevac helicopter was brought down by ground fire," Kimmitt said.

Kimmitt's remarks marked the first time any senior U.S. military official in Baghdad (search) has publicly acknowledged the helicopter was probably shot down.