PHILADELPHIA (AP) — One person died and two others were injured after an explosion damaged several homes on Philadelphia’s north side early Sunday, according to authorities.

Firefighters responded to a report of an explosion just before 5 a.m., according to the Philadelphia Fire Department.

Daniel McCarty, the department’s executive officer, said there was extensive damage to about five homes, including collapsed structures. One person died and two others who were rescued were hospitalized. McCarty said one was reported stable while the other was in critical condition.

Crews were expected to continue search and rescue operations.

“The biggest thing is the stability of the surrounding houses, making sure that this hazard doesn’t spread,” McCarty said. “This will be an extensive, all-day operation for the Philadelphia Fire Department.”

Authorities had not determined the cause of the explosion.