| WEST, Texas
WEST, Texas Rescuers searched on Thursday for survivors in the rubble of homes destroyed by a fiery fertilizer plant explosion in a small rural Texas town, as authorities struggled to determine how many people had been killed.
Concern and uncertainty gripped the town of West nearly a day after the chemical blast at West Fertilizer Co. injured more than 160 people. The cause of the explosion was not known and officials said no evidence of foul play had been found.
"All of that unknown ... is really scary, we don't know what has happened, who is alive, who is hurt, that's probably the worst part now," said Pat Lee, whose 92-year-old mother was injured in the blast on Wednesday evening.
Police initially put the death toll at up to 15, but later on Thursday Texas Department of Public Safety spokesman Jason Reyes told reporters that while the explosion had been deadly, it is not yet known how many had been killed.
While authorities stressed the Texas explosion could be an accident, it happened within days of the deadly Boston marathon bombings and the discovery of poisonous packages sent to President Barack Obama and a Republican senator - both incidents that have revived memories of the September 11, 2001, attacks.
Agents with the U.S. Chemical Safety Board, a federal agency that investigates industrial chemical accidents, and the Bureau of Alcohol, Tobacco, Firearms and Explosives are on the scene of the blast, which was the strength of magnitude 2.1 earthquake, according to the U.S. Geological Survey.
Fire-fighters had been battling a fire at the plant on Wednesday night for about 20 minutes before the blast rocked the town of 2,700 people about 20 miles (32 km) north of Waco. Three to four volunteer Fire-fighters were still missing, police said.
The blast destroyed 60 to 80 houses, reduced a 50-unit apartment complex to what one local official called "a skeleton standing up" and left a horrific landscape of burned-out buildings and blackened rubble.
Texas Governor Rick Perry described the situation as "a nightmare scenario." "The tragedy has most likely hit every family," he said.
Bryan Anderson, 41, injured along with his 9-year-old son Kaden near their home, said: "This doesn't happen in West, Texas. We are just a little town."
West has a strong Czech heritage, and the Czech Republic Embassy in Washington said on its website the ambassador was travelling to West, which is known among Texans as the place to stop on the highway between Dallas and Austin for kolaches, a popular Czech pastry.
'VERY VOLATILE SITUATION'
Police said the fertilizer plant was in a highly populated neighbourhood. "It is still a very volatile situation," said Chief Deputy Sheriff Matt Cawthon of McLennan County.
West Fertilizer Co is a retail facility that blends fertilizer and sells it to farmers. It stored 270 tons of ammonium nitrate, along with other "extremely hazardous" chemicals including anhydrous ammonia in 2012, according to a report the company filed with the state government.
Anhydrous ammonia is used by farmers as fertilizer to boost soil nitrogen levels and improve crop production.
According to the Centres for Disease Control, mixing anhydrous ammonia and water produces a poisonous cloud. When ammonia mixes with air, it forms an explosive mixture, and containers may explode when heated, according to the CDC.
The West plant is one of thousands of sites across rural America that store and sell hazardous materials such as chemicals and fertilizer for agricultural use, many within close range of residences and schools. The company is privately owned and has fewer than 10 employees.
The plant had not been inspected by state officials since 2006, when a complaint of an ammonia smell was resolved, said Zak Covar, executive director of the Texas Commission on Environmental Quality. State inspections are done only when there is a complaint, Covar said.
The federal Environmental Protection Agency fined the firm $2,300 (1,505 pounds) in 2006 for failing to implement a risk management plan.
The plant's owner could not be reached for comment.
Fire-fighters had been evacuating several blocks around the fire before the blast out of concern for dangerous fumes, police said. That threat had abated by Thursday, police said.
The West middle school, which was badly damaged, was one fifth of a mile from the plant and the high school was one-third of a mile away.
Perry declared McLennan County a disaster area and said he would request federal disaster aid from Obama. Obama, who flew to Boston for a memorial service for victims of the Boston bombings, offered support and prayers to the victims in Texas.
Texas is no stranger to industrial disasters. In 1947, 3,200 tons of ammonium nitrate fertilizer detonated aboard a ship in a Texas City port, killing almost 600 people, an incident believed to be the deadliest industrial accident in U.S. history.
More recently, a 2005 explosion at a BP refinery in Texas City killed 15 people and injured more than 170 others when hydrocarbon vapours exploded in a processing plant.
If the West blast was an industrial accident, investigators would look at whether Fire-fighters ignited the blast by pouring water on a volatile substance. Nim Kidd, chief of the Texas Division of Emergency Management, said it was too early to speculate.
"A lot of Fire-fighters will use their No. 1 tool, which is water, in a hazardous materials chemical situation to cool the surrounding environment," he told a briefing in Austin.
(Additional reporting by Nick Carey, Ian Simpson and Atossa Araxia Abrahamian, Lisa Maria Garza, Laura Heinauer and Mark Weinraub; Writing by Michelle Nichols and Ellen Wulfhorst; Editing by Doina Chiacu, Greg McCune and Philip Barbara)