At least 15 people are missing or dead and more than 150 injured after an explosion at a fertilizer plant in West , Texas, on Wednesday evening.

The explosion at West Fertilizer Co. began with a fire around 6 p.m. Volunteer firefighters were attempting to extinguish the blaze when an explosion ripped through the plant about two hours later. The blast registered as a magnitude 2.1 earthquake, according to federal seismologists.

Search and rescue operations were continuing and the death toll is only an estimate at this point, said Waco Police Sgt. William Patrick Swanton. Several volunteer firefighters are still missing on the scene, described by Swanton as “extreme devastation.”

At this time, Swanton said there was no indication that the explosion was anything other than an industrial accident. However, the federal Bureau of Alcohol, Tobacco, Firearms and Explosives has sent a team to the site to determine if the blast was “accidental or criminal,” a spokesman said. The U.S. Chemical Safety Board also deployed an investigatory team, and state officials set up air monitoring in the area.

Texas Department of Public Safety spokesman D.L.L Wilson said 50 to 75 homes were heavily damaged in the explosion, as well as a nearby apartment complex. More than 130 people were evacuated from a nearby assisted-living facility after the fire, before the explosion occurred.

A representative from Hillcrest Baptist Medical Center in Waco said that 101 people have been treated there, two in critical condition. Another 56 injured have been treated at nearby Providence Health Center. Most of the injured experienced burns or lacerations. Hospital staff have been advised that more injured may arrive as rescue operations find people trapped in the rubble.

Ongoing fires and the threat of toxic emissions and further explosions are hampering authorities’ search operations in the more heavily damaged areas near the blast site, an occurrence Texas industrial accident lawyers know is unfortunately not uncommon in this level of disaster. Door-to-door searches are planned eventually to scour the entire area for survivors.

The facility is located in the small Texas town, population of about 2,800, about 80 miles south of Dallas and close to Waco.