Explosion at NYC High School Injures Several

A thunderous gas explosion rocked a Manhattan high school building Thursday night, injuring three contractors – one critically – who were working to fix up the sixth floor science lab, authorities said.

The blast happened at the former John F. Kennedy High School in Marble Hill at around 8:10 p.m.

Mayor de Blasio, who showed up at the scene with FDNY Commissioner Daniel Nigro, called it a “shocking scene.”

“The sixth floor had tremendous damage. There will be a thorough investigation,” de Blasio said.

The explosion ripped through the fourth, fifth and sixth floors, blowing out windows and causing extensive damage.

An official who spoke to the injured workers said “a contractor was doing work with a blow torch and must have hit a gas line.”

Nearby resident Fein Fenner said, “It was the loudest noise I ever heard.”

“I ran away it was so loud. I thought it was a bomb.”

One worker, 36, was in critical condition and the other two, ages 53 and 38, were both in serious condition at Jacobi Hospital. All are expected to survive.

It was unclear if the building — which now serves six smaller high schools — would open in time for the fall semester, which begins Sept. 4.