The bodies of 14 people have been recovered from the remnants of a tiny Texas farm town that was rocked by a roaring explosion at a fertiliser plant, authorities have said, confirming for the first time the number of people who perished in the accident.
Officials did not identify those killed, but at least three of the dead were believed to be firefighters and other first-responders who rushed toward the West Fertiliser Co. to battle a fire that apparently touched off the blast.
They said on Friday about 200 people had been injured in Thursday's blast and that rescue teams continued searching through the rubble for survivors.
Sergeant Jason Reyes, of the Texas Department of Public Safety, said search efforts were ongoing, adding that the authorities had searched and cleared 150 buildings by Friday morning and still had another 25 to examine.
Officials said there was no indication of foul play in the blast at West Fertiliser Co, which they said had not been inspected since 2006, storing potentially combustible ammonium nitrate and was located in a residential area.
Sergeant William Patrick Swanton of Waco police said the plant was storing anhydrous ammonia in huge tanks. Anhydrous ammonia is used by farmers as fertiliser to boost nitrogen levels in soil and increase crop production.
According to the Center for Disease Control, anhydrous ammonia and water produces a poisonous cloud. When ammonia mixes with air, it forms an explosive mixture, and containers may explode when heated, according to the CDC.
The explosion, preceded by a fire at the plant, shook the ground with the strength of a small earthquake and levelled homes and businesses.
Flames shot into the night sky and rained burning embers, shrapnel and debris down on shocked residents.
"They are still getting injured folks out and they are evacuating people from their homes,'' Swanton said.
He added later: "At some point this will turn into a recovery operation, but at this point, we are still in search and rescue."
Swanton said officials went building to building in the largely decimated area around the plant.
"They have not gotten to the point of no return where they don't think that there's anybody still alive," he said.
Three to four volunteer firefighters were among those missing. Firefighters had been battling the blaze and evacuating nearby houses and a nursing home for about 20 minutes before the explosion occurred.
The US Chemical Safety Board, a federal agency charged with investigating industrial chemical accidents, was on the scene, as was the Bureau of Alcohol, Tobacco, Firearms and Explosives.
Al Jazeera's John Hendren, reporting from Texas, said the building where the explosion happened was still so hot that investigators had not been able to enter it.
He said many residents in the area had bought face masks to protect themselves, but that there had been no reports of anyone being hurt from inhaling toxic gas.
DL Wilson, Texas Public Safety Department spokesman, said about half the town, eight to 10 blocks, had been evacuated and that "we might even have to evacuate on the other side of town" if winds shift.
Ground motion from the blast, caused by a fire of unknown origin at the plant, registered as a magnitude 2.1 seismic tremor and created a jolt felt 130km away in Dallas, the US Geological Survey reported.
Wilson said 50 to 75 houses were damaged by the explosion and fire, and a nearby 50-unit apartment complex had been reduced to "a skeleton standing up".
The privately owned company had fewer than 10 employees.