A massive explosion at a fertiliser plant in the Texas town of West killed at least five to 15 people and injured more than 160 others, leaving the factory a smouldering ruin and levelling buildings for blocks in every direction.
Emergency workers searching through wreckage early today were bracing for the possibility that the toll would climb sharply.
The cause of the explosion is under investigation but it has left America reeling again, just two days after twin bombs in Boston killed three people and injured dozens.
"The school's gone, the apartments are gone," a young man in a blood-soaked T-shirt told reporters. "It's just horrible. Not something you ever want to have to deal with."
Resident Crystal Ledane told MSNBC how she fled with her children after the explosion blew out the doors and windows of her home.
"We just jumped in the car in what we had one. None of us had any shoes on, we just got out of there. Everything is just completely chaotic."
Earlier reports said at least nine people were killed, including six firefighters and a police officer.
The blast, around 8pm local time, rocked West, leaving people trapped and buildings on fire.
Flames and smoke erupted in the sky, and burning embers, shrapnel and debris rained down on shocked and frightened residents. The explosion could be heard 70km away.
Another bloodied, shaken resident, Dr George Smith, said: "There was just a major, major explosion. The windows came in on me, the roof came in on me, the ceiling came in. We lost all communication when the power went out. The whole street is gone."
A video filmed on a cellphone records the horror of a man and his daughter who were watching the drama unfold from a distance.
They had pulled over to the side of the road to watch the fire and the father was recording it on his phone. As the plant goes up, the blast envelops the outside of their car and the daughter can be heard screaming, "I can't hear ... get outta here. Please get out of here. Dad, please get out of here. I can't hear anything."
"Oh my god," the father replies.
West Mayor Tommy Muska told reporters that his city of about 2800 residents needs "your prayers."
"We've got a lot of people who are hurt, and there's a lot of people, I'm sure, who aren't gonna be here tomorrow. We're gonna search for everybody. We're gonna make sure everybody's accounted for. That's the most important thing right now."
A city councilman, Al Vanek, said a four-block area around the explosion was "totally decimated".
The toll included 50-75 houses, an apartment complex with about 50 units that one police officer said was reduced to "a skeleton," a school and the West Rest Haven Nursing Home, from which 133 patients, some in wheelchairs, were evacuated.
Other witnesses compared the scene to the 1995 Oklahoma City bombing that tore apart that city's Murrah Federal Building, killing 168 people, including 19 children in a daycare centre. Authorities said the West plant made materials similar to those used to fuel the bomb.
West's fire department was called to a blaze at the plant at 7.29pm. Muska, himself a volunteer firefighter, said the blast that followed knocked off his fire helmet and blew out the doors and windows of his home.
He said the main fire was under control by 11pm, but residents were urged to remain indoors because of the threat of new explosions or leaks of ammonia from the plant's ruins.
In the hours after the blast, many of the town's residents wandered the dark and windy streets searching for shelter. Among them was Julie Zahirniako, who said she and son Anthony had been playing at a school near the fertiliser plant when the explosion hit. She was walking the track, he was kicking a football.
The explosion threw her son 4 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 air.
"The fire was so high," she said. "It was just as loud as it could be. The ground and everything was shaking."
Erick Perez, 21, was playing basketball when the fire started. He and his friends thought nothing of it at first, but about a half hour later, the smoke changed colour. 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."
In the hours after the blast, entry into West was slow-going as the roads were jammed with emergency vehicles rushing to help.
Fires were still smouldering in the ruins of the plant and in several surrounding buildings.
Aerial footage showed injured people being treated on the flood-lit football field that had been turned into a staging area for emergency responders.
Councilman Vanek said first-responders were treating victims at about half a dozen sites, and he saw several injured residents from the nursing home being treated at the community centre.
Glenn A. Robinson, the chief executive of Hillcrest Baptist Medical Centre in Waco, told CNN that his hospital had received 66 injured people for treatment, including 38 who were seriously hurt.
He said the issues included blast injuries, orthopaedic injuries, large wounds and a lot of lacerations and cuts. The hospital had set up a hotline for families of the victims to get information, he said.
Debby Marak told the AP that when she finished teaching her religion class on Wednesday night, she noticed a lot of smoke in the area across town near the plant.
She said she drove over to see what was happening, and when she got there, two boys came running towards her screaming that the authorities had ordered everyone out because the plant was going to explode.
She said she had driven only about a block when the blast happened.
"It was like being in a tornado," Ms Marak said. "Stuff was flying everywhere. It blew out my windshield. It was like the whole earth shook."
She called her husband and asked him to fetch her. When they got to their home about 4km south of town, her husband told her what he'd seen: a huge fireball that rose like "a mushroom cloud".