Authorities are investigating why and how a military helicopter dropped a box of ammunition that crashed through the roof of an elementary school in El Paso, Texas.

KVIA-TV reports that a spokesman with the Ysleta Independent School District said no one was injured in the incident at Parkland Elementary School. It occurred Thursday afternoon after the school day was over and no students or staff were in danger.

Fort Bliss officials say the incident damaged the roof and a classroom.

"I'm extremely sorry for any damage done to the neighboring elementary school, and I am grateful that no one was injured,” Col. Jay Hopkins, commander of the 1st Armored Division Combat Aviation Brigade said in a news release. “The incident is under investigation.”
 
Fort Bliss said it will reassess its flight patterns to prevent similar incidents from happening.

The box made a hole in the roof and caused a power outage to a portion of the building, the district says.