William Burch and his wife, a retired Air Force nurse, entered the damaged nursing home before first-responders arrived. They searched separate wings and found residents in wheelchairs trapped in their rooms. The halls were dark, and the ceilings had collapsed. Water filled the hallways. Electrical wires hung eerily from the ceilings.
"They had Sheetrock that was on top of them. You had to remove that," Burch said. It was "completely chaotic."
Gov. Rick Perry called the explosion "a truly nightmare scenario for the community" and said he had been in touch with President Barack Obama, who promised his administration's assistance with operations on the ground.
Authorities said the plant made materials similar to those used in the 1995 Oklahoma City bombing.
The fertilizer used in that attack, ammonium nitrate, makes big explosions, be they accidental or intentional, said Neil Donahue, professor of chemistry at Carnegie Mellon University. It also was used in the first bombing attempt at the World Trade Center in 1993.
Ammonium nitrate is stable, but if its components are heated up sufficiently, they break apart in a runaway explosive chemical reaction, Donahue said.
"The hotter it is, the faster the reaction will happen," he said. "That really happens almost instantaneously, and that's what gives the tremendous force of the explosion."
About a half-hour before the blast, the town's volunteer firefighters had responded to a call at the plant, Swanton said. They immediately realized the potential for disaster because of the plant's chemical stockpile and began evacuating the surrounding area.
The blast happened 20 minutes later.
Erick Perez was playing basketball at a nearby school when the fire started. He and his friends thought nothing of it at first, but about a half-hour later, the smoke changed color. The blast threw him, his nephew and others to the ground and showered the area with hot embers, shrapnel and debris.
"The explosion was like nothing I've ever seen before," Perez said. "This town is hurt really bad."
The U.S. Chemical Safety Board was deploying a large investigation team to West. An ATF national response team that investigates all large fires and explosions was also expected, bringing fire investigators, certified explosives specialists, chemists, canines and forensic specialists. American Red Cross crews also headed to the scene to help evacuated residents.
Records reviewed by The Associated Press show the U.S. Pipeline and Hazardous Materials Safety Administration fined West Fertilizer $10,000 last summer for safety violations that included planning to transport anhydrous ammonia without a security plan. An inspector also found the plant's ammonia tanks weren't properly labeled.
The government accepted $5,250 after the company took what it described as corrective actions, the records show. It is not unusual for companies to negotiate lower fines with regulators.
In a risk-management plan filed with the Environmental Protection Agency about a year earlier, the company said it was not handling flammable materials and did not have sprinklers, water-deluge systems, blast walls, fire walls or other safety mechanisms in place at the plant.
State officials require all facilities that handle anhydrous ammonia to have sprinklers and other safety measures because it is a flammable substance, according to Mike Wilson, head of air permitting for the Texas Commission on Environmental Quality.
But inspectors would not necessarily check for such mechanisms, and it's not known whether they did when the West plant was last inspected in 2006, said Ramiro Garcia, head of enforcement and compliance.
That inspection followed a complaint about a strong ammonia smell, which the company resolved by obtaining a new permit, said the commission's executive director Zak Covar. He said no other complaints had been filed with the state since then, so there haven't been additional inspections.
The company could not be reached for comment. A call to the home of plant owner Don R. Adair rang unanswered.
The federal Chemical Safety Board has not investigated a fertilizer plant explosion before, but Managing Director Daniel Horowitz said "fertilizers have been involved in some of the most severe accidents of the past century."
He noted the 2001 explosion at a chemical and fertilizer plant that killed 31 people and injured more than 2,000 in Toulouse, France. The blast in a hangar containing 300 tons of ammonium nitrate came 10 days after the Sept. 11, 2001, terrorist attacks, raising fears at the time that the two could be linked. A 2006 report blamed the blast on negligence.
Horowitz also mentioned a disaster in Texas City in 1947, when a cargo ship holding more than 2,000 tons of ammonium nitrate caught fire and exploded, killing more than 500 people.
Associated Press writers Michael Brick, Will Weissert and Angela K. Brown and video journalist Raquel Maria Dillon in West; writers Jamie Stengle in Dallas, Ramit Plushnick-Masti in Houston and Seth Borenstein in Washington contributed to this report.
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