AlbSoft

The casualty count could spike to 60 or 70, said Dr. George Smith, the city's emergency management system director.

"We have two EMS personnel that are dead for sure, and there may be three firefighters that are dead," Smith said.

"There are a lot of people that will not be here tomorrow," Mayor Tommy Muska warned late Wednesday.

The explosion rocked the West Fertilizer Co. at about 7:50 p.m. (8:50 p.m. ET). It's being treated as a crime scene until investigators determine whether it was an accident. "Nothing at this point indicates we have had criminal activity, but we are not ruling that out," said Sgt. William Patrick Swanton of the nearby Waco Police Department.

Swanton estimated the death toll as high as 15.

Patients were rushed to several hospitals. Hillcrest Baptist Medical Center reported five patients in intensive care -- two in critical condition, three in serious condition. At least 28 patients will be admitted, said hospital chief Glenn Robinson.

About half the community of 2,800 was evacuated, Muska said.

The White House said it is monitoring the situation through FEMA, which is in touch with state and local authorities.

'Like a nuclear bomb'

The blast shook houses 50 miles away and measured as a 2.1-magnitude seismic event, according to the United States Geological Survey.

"It was like a nuclear bomb went off," Muska said. "Big old mushroom cloud."

Firefighters painstakingly combed damaged homes, many which had been reduced to rubble.

"(It's) massive -- just like Iraq. Just like the Murrah (Federal) Building in Oklahoma City," said D.L. Wilson of the Texas public safety department.

The blast stripped a nearby apartment complex, with 50 units, of its walls and windows. "It was just a skeleton standing up," Wilson said.

A nursing home, with 133 residents, was quickly evacuated. A middle school also is located near the plant.

"There are lots of houses that are leveled within a two-block radius," Smith said.

Weather could hamper efforts

A storm system heading into the area could worsen the situation.

"Winds will be gusting up to 35 miles per hour through the afternoon," said CNN Meteorologist Jennifer Delgado. "This can move the direction of the fire" -- a big concern for firefighters working to contain the blaze, she said.

Lightening and hail could damage those efforts as well -- and endanger people in the area who've been left homeless.

Overnight lows will be just above freezing, Delgado said. Those without homes will need shelter.

West is about 75 miles south of Dallas and 120 miles north of Austin. The town's chamber of commerce touts it as "the Czech point of central Texas."

Czech immigrants arrived in the town in the 1880s, and the community still maintains strong ties to their central European roots, with businesses named "Little Czech Bakery" and "The Czech Inn."

The explosion: What we know so far

'The roof came in on me'

The blast sent a massive fireball into the sky. Flames leaped over the roof of a structure and a large plume of smoke rose high into the air.

"The windows came in on me, the roof came in on me, the ceiling came," said George Smith, the city EMS director.

Brad Smith lives 50 miles away and felt his house shake.

"We didn't know exactly what it was," he said. "The forecast said a line of thunderstorms was going to come though. My wife and I looked up and wondered, 'Did it get here six hours early?'"

Five hours after the blast, carloads of the wounded continued to stream into hospitals.

While some of the injuries are minor, others were "quite serious," said Robinson of Hillcrest Hospital in Waco.

Many suffered from "blast injuries, orthopedic injuries (and) a lot of lacerations," he said.

Risk remains

For the town, the danger may not be over.

Even though officials have turned off all the gas, they worry another tank at the facility might explode.

Volunteer firefighters head toward danger despite personal tragedy

"What we are hearing is that there is one fertilizer tank that is still intact at the plant, and there are evacuations in place to make sure everyone gets away from the area safely in case of another explosion," said Ben Stratmann, a spokesman for Texas State Sen. Brian Birdwell.

If the winds shift, the other half of the town will have to be evacuated as well.

The big concern: anhydrous ammonia, a pungent gas with suffocating fumes that is used as a fertilizer.

When exposed to people, the gas can cause severe burns if it combines with water in the body.

Exposure to high concentrations can lead to death.

The West Fertilizer Co. said it had 54,000 pounds of the chemical, The Dallas Morning News reported.

What is anhydrous ammonia

The scene

Early Thursday morning, state troopers in gas masks manned roadblocks, waving away cars coming off the highway.

The Federal Aviation Administration instituted a flight restriction over the town.

Authorities closed schools for the rest of the week, and urged everyone to stay away from school property.

So many firefighters and medics descended on the town to help its all-volunteer force that the public safety department pleaded that no more assistance was needed.

"The firefighters and EMS people are coming from hundreds of miles away to help us," Wilson said. "Right now, we are overflowing with help. "

Worst-case scenario

In 2006, West Fertilizer had a complaint filed against it for a lingering smell of ammonia, the Texas Commission on Environmental Quality website shows.

Separately, the plant had informed the Environmental Protection Agency that it presented no risk of fire or explosion, according to The Dallas Morning News. It did so in an emergency planning report required of facilities that use toxic or hazardous chemicals.

The plant's report to the EPA said even a worst-case scenario wouldn't be that dire: there would be a 10-minute release of ammonia gas that wouldn't kill or injure anyone, the newspaper reported.

But what happened Wednesday night was much worse.

Tommy Alford, who works in a convenience store about three miles from the plant, said several volunteer firefighters were at the store when they spotted smoke.

Alford said the firefighters headed toward the scene and then between five and 10 minutes later, he heard a huge explosion.

"It was massive; it was intense," Alford said.

'Not the end of the world'

Cheryl Marak, who sits on West's city council, said the blast's impact knocked her to the ground.

"It demolished both the houses there, mine and my mom's and it killed my dog," she said.

Other residents had similar stories.

"It was like a bomb went off," said Barry Murry, who lives about a mile from the plant. "There were emergency vehicles everywhere. It has been overwhelming."

As they waited for daybreak, they sought comfort in each other and in Mayor Muska's words.

"This is not the end of the world," he said. "This is a big ol' cut that we got across our hearts right now."

"But," he added, "we are strong. We will rebuild."