(WEST, Texas) -- A fire and chemical explosion at a Texas fertilizer plant in a small town north of Waco, Texas, killed an estimated five to 15 people, sent at least 180 to hospitals, flattened buildings and prompted widespread evacuations.
The initial blast at the West Fertilizer Plant in West, Texas, occurred just before 8 p.m. Wednesday, but officials still were struggling to tally the dead and injured early Thursday morning and were searching door-to-door amid the rubble for survivors, Sgt. William Patrick Swanton of the Waco Police Department said.
Of the estimated death toll, Swanton told reporters Thursday morning, "I know that's a rough estimate, but that's the best that I can give you."
West EMS Director Dr. George Smith, himself injured and bloody, said he had not personally seen bodies to confirm deaths, but believed the blast killed at least two emergency responders to a fire at the plant before the initial explosion and a person at a nearby apartment complex that suffered serious damage.
In addition, some responders to the fire were believed unaccounted for after the blast, according to Smith, Swanton and West Mayor Tommy Muska.
As they gained access to the explosion site, officials said they were treating it as a crime scene.
"We are not indicating that it is a crime, but we don't know," Swanton said. "What that means to us is that until we know that it is an industrial accident, we will work it as a crime scene. ATF [the federal Bureau of Alcohol, Tobacco, Firearms and Explosives] is conducting the main investigation."
The disaster even drew condolences from Pope Francis, who tweeted, "Please join me in praying for the victims of the explosion in Texas and their families."
Earlier concerns about the possibility of dangerous ammonia fumes and shifting winds were subsiding Thursday morning as fires died down, Swanton said.
"Air quality, at this point, is not an issue," he said. "It is not a concern."
Nevertheless, numerous other concerns remained.
Witnesses reported heavy fire or concussive damage to a middle school, homes and an apartment complex near the plant, as well as to a nursing home, where more than 130 residents were evacuated, according to Muska.
Buildings in a radius of about five blocks around the plant -- including at least 60 more homes -- were heavily damaged by the blast, officials said.
"It was almost tornadic in effect," Swanton said. "It looked like to me one home would be fine and next to it there would be extreme devastation."
State Trooper D.L. Wilson of the Texas Department of Public Safety described the initial fertilizer plant blast as "massive -- just like Iraq, just like the Murray Building in Oklahoma City. The same kind of hydrous [ammonia] exploded, so you can imagine what kind of damage we're looking at."
The blast even registered as a 2.1 magnitude seismic event, according to the U.S. Geological Survey.
It was felt 20 to 30 miles away, witnesses said, and near the plant burned buildings, knocked down people, blew out windows and, according to Wilson, left the damaged apartment complex looking like "just a skeleton standing up."
By 5:45 a.m. ET, hospitals near the blast site reported treating 180 people. At least 16 patients at the hospitals were in critical condition and three in serious condition.
Hillcrest Baptist Medical Center in Waco, Texas, saw more than 100 of the wounded, officials there said. Patients from the blast also were confirmed early Thursday at Providence Healthcare Network in Waco, Parkland Hospital in Dallas, and Scott & White Memorial in Temple, Texas.
The fertilizer plant exploded around 7:50 p.m. local time Wednesday, according to the Texas Department of Public Safety.
Emergency response audio told the story of the chaos among firefighters and others at the scene.
"We need every ambulance we can get this way," one snippet said. "A bomb just went off. It's pretty bad."
"Firefighters down," another said. "There has been an explosion."
There were subsequent explosions around 10 p.m., ABC News affiliate WFAA-TV reported. The cause of the explosions was unconfirmed, but a dispatcher was heard warning crews to move away from chemicals in unexploded tanks.
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