Explosion Rocks New York City High School, Injuring At Least 3, Officials Say

— -- A massive gas explosion rocked a New York City high school Thursday night, injuring at least three people, fire officials said.

The blast occurred at JFK High School in The Bronx just after 8 p.m. and hundreds of firefighters responded, according to the FDNY.

It's unclear what sparked the explosion, which damaged the 4th-6th floors of the school.

Three people were taken to a local hospital - one was in critical condition and two were in serious condition, authorities said.

Witnesses said the blast rattled windows and set off car alarms, according to ABC-owned station WABC.