NEW YORK (CBSNewYork) — Three workers were injured Thursday night when an explosion severely damaged a high school in the northwest Bronx late Thursday.

The explosion was reported at 8:09 p.m. Thursday night on the sixth floor at John F. Kennedy High School, at 99 Terrace View Ave.

The school is located on the western edge of the neighborhood of Marble Hill — which is politically part of Manhattan, but geographically in the Bronx. The Department of Education considers the school to be in the Bronx.

As CBS2’s Valerie Castro reported, officials said the explosion happened during construction work in a sixth floor science lab at the school. Three workers suffered severe burns.

At least three floors of the building were heavily damaged, officials told CBS2. Photos at the scene showed windows blown out and other interior and exterior damage.

“This school obviously has sustained some very, very serious damage,” Mayor Bill de Blasio said at the scene. “This was part of a project being run by the school construction authority through a private contractor.”