DALLAS - A massive explosion at a fertilizer plant rocked a Texas town north of Waco, causing multiple casualties and leaving people trapped and buildings on fire.

Emergency personnel were bracing for the possibility of dozens of dead and many more injured in the blast, which occurred before 8 p.m. in the town of West and could be heard 45 miles away in Waxahachie.

Although authorities confirmed that people had been killed, after midnight they were still saying they did not have an official toll. However, Department of Public Safety spokesman D.L. Wilson did estimate that more than 100 people had been injured.

Firefighters were reportedly among those who could not be accounted for after the explosion, about 80 miles south of Dallas.

A blaze had broken out earlier at the plant, and the explosion occurred while firefighters were trying to put it out.

"It was a small fire and then water got sprayed on the ammonium nitrate, and it exploded just like the Oklahoma City bomb," said Jason Shelton, a clerk at the Czech Best Western Hotel in West. "I live about a thousand feet from it and it blew my screen door off and my back windows. There's houses leveled that were right next to it."

Authorities were evacuating residents of the town of 2,600, including occupants of a nearby nursing home that was badly damaged in the blast that had spread debris across a wide area.

Numerous buildings were on fire, including the nursing home and West Middle School. Everything around the plant had been blown apart or collapsed, including a nearby apartment complex that had been destroyed.

"That whole side of town looks like a disaster," resident Bill Manolakis said. "Who in their right mind sticks a damn plant next to houses?"

The disaster prompted a massive deployment of law enforcement and emergency personnel from the region.

Hospitals as far as Temple had been asked to prepare for hundreds of patients, and numerous emergency helicopters had been dispatched to assist, though high winds were hampering their flights.

Hillcrest Baptist Medical Center in Waco had received nearly 100 patients who arrived in ambulances and private vehicles, said the hospital's chief executive, Glenn Robinson. He said more than 40 people were in serious condition, with injuries including blast wounds and large lacerations.

Bill Bohannan told the Waco Tribune-Herald he witnessed the devastating blast while visiting his parents' home near the plant.

"I was standing next to my car with my fiancée, waiting for my parents to come out and (the plant) exploded," he said. "It knocked us into the car … Every house within about four blocks is blown apart," he said.

People as far away as 50 miles reported feeling what seemed like an earthquake.

Witnesses described a chaotic scene, with rescuers and evacuees scrambling as traffic backed up for miles on Interstate 35 and livestock ran loose.

The American Red Cross was sending teams from throughout the region and was working to find shelter for the evacuees.

Gov. Rick Perry said state officials also were monitoring developments.

"We are … gathering information as details continue to emerge about this incident," he said. "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."