WEST, Texas: Hundreds of people were likely injured in a fiery explosion on Wednesday night at a fertiliser plant near Waco, Texas, that damaged or destroyed numerous buildings including a school and nursing home, authorities said.

The blast was reported at about 8 pm CDT (0100 GMT on Thursday) in West, a town of some 2,700 people about 80 miles (130 km) south of Dallas and 20 miles (32 km) north of Waco.

“It's a lot of devastation. I've never seen anything like this,” said McLennan County Sheriff Parnell McNamara. “It looks like a war zone with all the debris.”

There was no immediate official word on what sparked the explosion as emergency personnel assisted victims and doused the flames.

A spokesman for the Texas Department of Public Safety, D.L. Wilson, told Reuters the blast had probably caused “hundreds of casualties” and damaged many homes. He added that a nearby nursing home had collapsed from the explosion and that people were believed trapped inside.

McNamara said the nursing home and much of the center of town had been evacuated, and that residences near the explosion had been leveled.

The air in town remained thick with smoke more than two hours after the explosion, and the area around the blast site was littered with shards of wood, bricks and glass.

A Reuters reporter observed that a nearby middle school and several homes were severely burned. Dallas television station WFAA reported from helicopters that roughly a three-block area of West appeared to have been destroyed.

More than 100 people were being taken to Hillcrest Baptist Medical Center in Waco, said vice president of hospital operations David Argueta.

Hillcrest CEO Glenn Robinson told CNN that the hospital was seeing “everything from orthopedic injuries to patients that are experiencing serious blood loss.”

Governor Rick Perry issued a statement saying his office had “mobilised state resources to help local authorities” deal with the incident.

A White House official said the Obama administration was aware of the situation and monitoring local and state response through the Federal Emergency Management Agency.

The explosion came two days before the 20th anniversary of a fire in Waco that engulfed a compound inhabited by David Koresh and his followers in the Branch Davidian sect, ending a siege by federal agents.

Some 82 members of the sect and four federal agents died at Waco.