Authorities are trying to determine how a box of ammunition fell from a military helicopter and crashed through the roof of an elementary school in Texas.

The Ysleta Independent School District said no one was injured when the ammo box hit Parkland Elementary School in El Paso on Thursday afternoon. The ammo box left a hole in the roof and caused a power outage in part of the building.

US military parachute part lands by school in Japan Days after local residents near Yokota Air Base, Japan, protested the arrival of five Air Force CV-22 Osprey tiltrotor aircraft due to safety concerns, part of a military parachute landed on the grounds of a nearby school.

Officials at nearby Fort Bliss said they’ll reassess flight patterns as part of their investigation.

In a statement, 1st Armored Division Combat Aviation Brigade commander Col. Jay Hopkins said he was sorry for the damage and grateful no one was hurt.