BUFFALO, N.Y. — A firefighter battling a large fire in Buffalo, New York on Wednesday became trapped in a partial building collapse and remained unaccounted for hours later, officials said.

Firefighters responded to the fire in the downtown commercial district at about 10 a.m., Buffalo Fire Commissioner William Renaldo said.

“Quickly thereafter there was a mayday call,” Renaldo said. “There was a structural collapse, an interior collapse. Firefighters had to evacuate. And unfortunately one of our firefighters was trapped and is still trapped, and we’re still trying to make our way to that firefighter as we speak.”

Videos of the fire scene show firefighters appearing to be knocked down by a sudden blast or explosion as smoke billows out of the burning building.

Renaldo said at a briefing Wednesday afternoon that firefighters had not had any contact with their missing colleague since the firefighter became trapped.

Asked if the firefighter might still be alive, Renaldo said. “There is a possibility, yes. We’re keeping that hope.”

Buffalo Mayor Byron Brown said, "Certainly our thoughts and hopes and prayers are that the firefighter will make it out of this fire. This is a difficult day in the city of Buffalo, and certainly we are asking for prayers.”

The cause of the fire was under investigation. Renaldo said his department was investigating a report that workers had been seen with torches near the building, which was being renovated.