Authorities in Texas estimate between five and 15 people have been killed by a massive explosion at a fertilizer plant near the city of Waco.
Waco police Sergeant William Patrick Swanton also told reporters that more than 160 people have been injured.
The cause of the April 17 blast in the community of West, some 32 kilometers north of Waco, was not immediately known.
But Swanton said the area will be treated as a crime scene until authorities complete their investigation.
"I have heard no indications that this was anything other than an accidental fire," Swanton said. "However, the investigators in this case have not been able to get inside and see, determine what the source of the fire was, where it came from, whether it was intentionally set or whether it was not. They don't know."
Mayor Tommy Muska spoke late on April 17, describing the scene when he arrived.
"The plant was on fire prior to the explosion," Muska said. "It was fully engulfed when I arrived and then it blew up."
Firefighters had attempted to put out the fire before the plant exploded and and authorities say three or four firefighters have not been accounted for.
Muska said at least 50 homes were destroyed but added the community of some 2,800 people would recover.
"There [are] a lot of people that got hurt. There's a lot of people that I'm sure are not going to be here tomorrow. So, your prayers -- this is a very, very strong community. We will bounce back," Muska said. "This is probably the major, most devastating thing that has happened to this community. But we're going to build back. It's not the end of the world, it's just a big old cut that we got across our hearts. So, we're going to search for everybody. We're going to make sure everyone is accounted for. That's the most important thing right now."
Authorities say it is unclear how many people may still be trapped in the rubble, as the search for victims is continuing. Video from the scene showed a gigantic blast at the plant, billowing smoke, and raging fires.
Hospital officials said some of those injured suffered serious burns.
The U.S. Geological Survey said the explosion caused a 2.1-magnitude tremor.
Texas Governor Rick Perry issued a statement saying his office had "mobilized state resources to help local authorities" respond to the incident.
Governor Perry later described the situation as a "truly nightmare scenario."
He has declared the county an emergency disaster area and will request federal funds.
U.S. President Barack Obama on April 18 issued a statement of support for the people of West.
"West is a town that many Texans hold near and dear to their hearts, and as residents continue to respond to this tragedy, they will have the support of the American people," he said.
With reporting by Reuters, AP, and AFP