Crews sifting through debris of a powerful explosion and fire that gutted a Maryland apartment building recovered two bodies Thursday and were looking for others still missing, officials said.
The identities of the victims at the Silver Spring complex were still not known, said Montgomery County Assistant Police Chief Russ Hamill, and it was unclear exactly how many people were not found amid the chaos.
Related: More coverage on NBC Washington
"As a result of this discovery, this scene and event will be handled as a death investigation," Hamill told reporters.
Police earlier said five to seven peole could not be located following the blast at the Flower Branch Apartments, which was rocked just before midnight Wednesday. Rescue dogs were being used to search the rubble, although parts of the four-story apartment building needed to be secured before investigators could go inside.
The blast was so powerful, according to regional disaster director Paul Carden, that many people were "blown out of their beds."
More than 160 fire and rescue workers were called to the scene to help fight a fire that followed the blast, Montgomery County Fire Chief Scott Goldstein said.
Thirty-one people were transported to the hospital in addition to three firefighters who had non-life-threatening injuries. The firefighters were treated and released.
Kitchens in the building's apartments were reportedly fitted with stoves powered by natural gas.
Hamill said residents noted smelling gas before the explosion, but that the investigation is still in its "very preliminary stages."
Video taken from the scene early Thursday showed firefighters continuing to hose down the charred debris of the brick building. Rows of windows appeared blown out and belongings were strewn in nearby tree branches and piled on the ground.
Montgomery County Fire and Rescue Chief Dorcus Howard Richards told The Washington Post that firefighters in a nearby station heard the explosion and were on the scene quickly.
When firefighters arrived, they received reports of people trapped inside, said Montgomery County Fire Capt. Oscar Garcia.
Officials declared the scene a "mass casualty incident," NBC Washington reported.
In total, 98 residents have been displaced from 28 apartments, Goldstein told reporters.
The building is home to many residents who speak Spanish and translators were being brought onto the scene to assist families.
Among the 31 residents hospitalized, injuries ranged from broken bones to smoke inhalation and burns.
"People were dropping children and jumping out of other windows,'' Goldstein said. "Everybody was getting out of the building as rapidly as possible.''
One unnamed woman at the scene told NBC Washington that she was searching for her uncle after her calls to his cellphone went unanswered.
"He lived in the building that collapsed. We're here waiting and nobody tells us, nobody say anything to us," she said.
The explosion hit like an earthquake, resident Carlos Ingles told NBC Washington. He said instead of fleeing the flames, he tried to help others who couldn't find their way out.
"Children, they were thrown from the top," he said. "I don't have words."