A mortar shell that exploded as several schoolchildren played with it killed two of the boys and injured six others in central Vietnam.

Village official Nguyen Sy Thong said Wednesday that the boys picked up the shell on their way to school in the central highland province of Dak Nong.

Two 11-year-old boys died in a hospital after the explosion Tuesday and their six male classmates were hospitalized with serious injuries.

Thong said the area was an American base during the Vietnam War and became a military firing range after the war ended in 1975.

Police are investigating whether the shell was left over from the war or by the military when they were using the area to practice shooting.