An explosion at a fertilizer plant in Texas last night powerful enough to cause a magnitude 2.1 earthquake has killed up to 15 people – and possibly more.

The casualty rate is expected to rise, according to press reports. A number of firefighters are among those still missing after the blast. (Firefighters – including volunteers – were at the plant fighting the blaze when the explosion occurred.) Two EMS personnel are confirmed dead.

The explosion occurred at the West Fertilizer Co. in West, Texas, a town of 2,700 residents about 20 miles north of Waco.

At least 160 people were injured. Sources at local hospitals said at least 38 people are listed in serious condition, in addition to nine burn victims who were rushed to a Dallas burn center. In addition to broken bones and abrasions, many of the injured suffered from chemical or smoke inhalation.

The incident shook houses 50 miles away, blasted off the walls and windows of a nearby apartment complex and leveled buildings in a six-block radius around the facility . It measured as a 2.1-magnitude seismic event, according to the United States Geological Survey. The 133 residents of a nearby nursing home were evacuated.

Firefighters combed through the rubble of homes into the night, looking for survivors. A late night thunderstorm added to the misery at the scene.

Residents were urged to remain indoors after the fire was brought under control around 11 p.m. out of concerns about leaks of ammonia from the plant, but authorities early this morning dismissed those concerns.

Texas Governor Rick Perry released the following statement:

“We are monitoring developments and gathering information as details continue to emerge about this incident. We have also mobilized state resources to help local authorities. Our thoughts and prayers are with the people of West, and the first responders on the scene.”

Because the cause of the fire and explosion are unknown, the area is being treated as a crime scene, with the federal Bureau of Alcohol, Tobacco, Firearms and Explosives leading the investigation. President Obama was briefed on the incident and is monitoring the situation with FEMA.

The Huffington Post is reporting that the West Fertilizer Co. was cited in 2006 for failing to obtain or to qualify for a permit. The Texas Commission on Environmental Quality investigated the company after receiving a complaint from a local resident about a strong ammonia smell.