Among those believed to be dead were three to five volunteer firefighters. The many injuries included broken bones, cut and bruises, respiratory problems and minor burns. Five people were reported in intensive care.
In the hours after the blast, residents wandered the dark, windy streets searching for shelter. Among them was Julie Zahirniako, who said she and her son, Anthony, had been at a school playground near the plant when the explosion hit.
The explosion threw her son four feet in the air, breaking his ribs. She said she saw people running from the nursing home, and the roof of the school lifted into the sky.
"The fire was so high," she said. "It was just as loud as it could be. The ground and everything was shaking."
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."
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, said Neil Donahue, professor of chemistry at Carnegie Mellon University.
"The hotter it is, the faster the reaction will happen," Donahue said. "That really happens almost instantaneously, and that's what gives the tremendous force of the explosion."