Three blank rounds were found on the campus of a junior high school in Oyama, Shizuoka Prefecture, and the U.S. Army reported to the South Kanto Defense Bureau that one of its helicopters mistakenly dropped three blank cartridges during a drill at the foot of Mount Fuji.

A student of Oyama Junior High School found the bullets on a tennis court Tuesday and the school notified the police. The 7-cm-long bullets, 1.2 cm in diameter, are believed to be blank cartridges used in autoloading rifles, according to police. No injuries were reported.

The U.S. Army reported the helicopter's mishap to the South Kanto Defense Bureau on Wednesday.

The U.S. military had submitted to the Oyama Municipal Government its plan to conduct a drill at the Ground Self-Defense Force's East Fuji Maneuver Area between last Sunday and this Saturday.

The South Kanto Defense Bureau said the U.S. military is investigating the case to prevent similar incidents.