OAK CLIFF — A gas explosion destroyed a Dallas apartment complex in the Oak Cliff neighborhood Thursday afternoon, killing an unknown number of people and leaving at least 11 residents unaccounted for. The blast occurred just before 1 p.m. at a two-story building located at the intersection of Patton Avenue and East 9th Street.

The explosion followed a gas leak caused when a contractor working at the site struck a natural gas pipeline, according to Atmos Energy. The company was notified by the fire department at 12:51 p.m. that “a construction crew unrelated to Atmos Energy damaged a natural gas pipeline near 409 E. 9th Street.” Natural gas service in the immediate area has since been shut off, and Atmos Energy technicians are assisting first responders at the scene.

Dallas Fire-Rescue initially responded to a gas leak call, but the situation escalated from a two-alarm to a five-alarm fire after an explosion occurred while responders were en route. “Our first responders, while they were en route to that gas leak, a subsequent explosion occurred,” Deputy Chief Mark D. Berry said. He confirmed fatalities, stating, “There have been fatalities at this point.”

The operation has transitioned from rescue to recovery mode. “This is an active incident still, it’s still under investigation, there’s still phone calls that haven’t been answered,” Berry said. He added, “We may be in this mode for the next two to four hours, maybe extending this operation even beyond that.”

At least four people were hospitalized following the explosion, though their conditions are unknown. Video from the scene showed the building’s roof collapsed, walls covered in ash, and debris scattered across the street. Windows in neighboring buildings appeared blown out, and a large plume of black smoke rose above the site. Nearly 100 firefighters responded to the blaze.

A family reunification center has been established at W. H. Adamson High School.