An American military investigative team is trying to determine whether some of the Marines killed in a battle with Iraqi troops Tuesday were accidentally hit by U.S. or allied forces.

Marine Lt. Col. Jerry Humble said late Thursday that the four-man Marine team includes a munitions expert who will examine the hulk of the light armored vehicle in which an unspecified number of Marines was killed.Eleven Marines - including Lance Cpl. Dion James Stephenson of Bountiful, Utah - died in the fighting.

A Pentagon source in Washington said Friday that one reason for the investigation is that a hole in one of the Marines' vehicles came from a 30mm gun, which is the weapon aboard the Air Force's A-10 anti-tank "Wart-hog." The source insisted on anonymity.

Humble, operations officer for the 1st Marine Division, said, "We're saddened and disappointed" about the possibility of deaths caused by friendly fire. "But historically, there's always casualties by friendly fire in close battles because it's a fight for your life."

Marines and Iraqi ground forces were locked in close combat during much of Tuesday's fighting, and U.S. Air Force A-10 and other aircraft were called in to provide air support.

Meanwhile in Washington, Sen. Jake Garn, R-Utah, received a call from Jim Stephenson about how proud he was of his 22-year-old son in the American cause.

Garn said, "Considering how difficult it is for a parent to lose a child, I am touched by Mr. Stephenson's attitude and perspective. I am very proud that he is able to feel like this at such a personally trying time."