Authorities say three people were injured when a gas line exploded during construction at a high school in the Bronx.

Fire officials say it happened at about 8 p.m. Thursday at John F. Kennedy High School in the Marble Hill neighborhood. Nearly 140 firefighters responded to the scene.

Police say the injuries were not considered life-threatening. All three were taken to Jacobi Hospital.

A police spokesman said crews were working on a gas line when the explosion occurred. Fire officials say gas to the building has been shut off.

Utility crews were at the scene. A Con Ed spokesman says the explosion happened on the sixth floor.

The school serves more than 1,200 students in grades 9-12. The first day of school is Sept. 9.