HOUSTON - A fire is still burning at a Texas fertiliser plant, six hours after an explosion Wednesday night is feared to have killed dozens and injured 170 more, but emergency services say they now have it under control.

The explosion happened about 7:50 pm local time (0050 GMT Thursday) in the city of West, some 320 kilometers north of the Texas capital of Houston.

The remains of a fertilizer plant burn after an explosion at the plant in the town of West, near Waco, Texas early April 18, 2013. [Photo/Agencies]

There are no official casualty figures, but Dr. George Smith, the head of Texas Emergency Medical Services in West, said at least 60 were dead and more than 100 injured, KWTX broadcaster reported.

West Mayor Tommy Muska told an earlier news conference it had been confirmed at least four or five rescuers and firefighters were missing.

Muska said a fire broke out at the fertilizer plant before the explosion, which devastated surrounding areas, destroying 10 homes and damaging 50 more. It also triggered a 2.1-magnitude earthquake.

Rescuers launched a door-to-door search overnight for dead and injured residents.

Authorities are also concerned toxic chemicals may have been released into the air.

The cause of the initial fire and explosion are still being investigated.

West is a small city of 2,600 residents. Half of the town was evacuated after the explosion.