Dallas (AP) — A huge fire destroyed a two-story apartment building in Dallas on Thursday, causing fatalities and injuring at least four people, and the search for the missing is ongoing, a fire official said.

The blaze sent huge plumes of black smoke into the sky and drew a massive firefighter response.

“There have been fatalities at this point,” Dallas Fire-Rescue Deputy Chief Mark Berry said at a news conference, adding the mission has changed from rescue to recovery. “Let us work through the recovery phase and get a total number.”

Dozens of firefighters searched through the smoldering rubble of the building on the outskirts of downtown Dallas Thursday afternoon, even as colleagues continued to drench the blackened debris.

Berry said firefighters were responding to a call of a gas leak when an explosion happened.