(For further background, read our second story as industry experts analyze possible causes.)
A fertilizer plant exploded late Wednesday in West, Texas, killing between 5 and 15 people, injuring at least 160 and destroying dozens of homes and businesses in the town, according to the latest media reports.
Waco Police Sgt. William Patrick Swanton said at a Thursday morning briefing that the fire and blast appeared to involve a railroad tanker carrying anhydrous ammonia.
The incident began with a fire at the West Fertilizer Co. plant that began around 6 p.m. local time Wednesday night. Volunteer firefighters in the town of about 2,800 people, located 80 miles south of Dallas, tried to extinguish the fire.
About two hours later, a thunderous explosion ripped through the plant, registering as strong as a magnitude 2.1 earthquake, according to federal seismologists. It sent a column of smoke hundreds of feet into the air.
The facility was located close to homes and an apartment complex, where many of the injuries occurred. There is an assisted-living facility close by, but more than 130 people had been evacuated from it after the fire broke out but before the explosion.
Swanton said the death toll was only an estimate as search-and-rescue operations are ongoing. The whereabouts of several volunteer firefighters remain unknown. He described a scene of "extreme devastation" near the site of the explosion and added he expected there would be a rising list of fatalities.
Swanton added that there is no indication the blast was anything other than an industrial accident.
The US Chemical Safety Board (CSB) said it was deploying a large investigation team to the scene. "Local emergency officials have told the CSB of a large number of injuries and destroyed buildings in the town," the board said in a statement.
Texas state officials have set up air monitoring nearby, though officials said it did not appear that West was threatened by chemical fumes from the plant.
Even so, reports said about half of the town of 2,800 was evacuated due to damage or the threat posed by the fumes, and the "other half" of West might soon be evacuated, as winds are expected to shift.
In 2006, West Fertilizer applied for a permit for two existing 12,000-gal anhydrous ammonia storage tanks, according to the Texas Commission on Environmental Quality. It is unclear from the document when the tanks were installed.
The state agency's report highlighted the facility's proximity to populated areas, noting it must be equipped with a water-spray system to address accidental emissions and remarking it was within 3,000 feet of a school. The same year, the US Environmental Protection Agency fined the company $2,300 for failing to implement a risk-management plan, according to an EPA database.
The fertilizer plant was formerly known as West Chemical & Fertilizer and was also known as Texas Grain Storage Inc., according to a 2007 federal court filing. It was started by the Plasek family in 1957 as a grain-storage business.
In 1960, Texas Grain Storage added a small fertilizer blend plant for farmers in the area and started selling fertilizer and grain-storage services for other farmers in Texas
-- Additional reporting by Dow Jones Newswires