Rescuers and paramilitary police officers walk today amid the rubble of damaged houses in Viareggio, after a freight train exploded just outside the station of this coastal town in northern Italy. A rail car filled with liquified natural gas exploded when a freight train derailed in the middle of a small Italian town, setting off an inferno. At least 12 people were killed and at least 50 injured.

VIAREGGIO, Italy — A freight train derailed and plowed into houses in a small Italian town, setting off an explosion and fire that killed at least 12 people — many as they slept in their homes — and injured at least 50, officials said today.

The 14-car train was traveling from the northern city of La Spezia to Pisa when a rear car derailed and crashed into a residential neighborhood beside the train station in the Tuscan seaside town of Viareggio just before midnight Monday.

A train car filled with liquified natural gas exploded, collapsing five buildings and setting fire to a vast area. Homes crumbled or burned, killing residents as they slept.

The exact death toll was unclear as hundreds of rescuers searched through the rubble for survivors.

Many of the injured suffered severe burns.

"We saw a ball of fire rising up to the sky," said witness Gianfranco Bini, who lives in a building overlooking the station. "We heard three big rumbles, like bombs. It looked like war had broken out."

His son, Gianni Bini, said he saw a truck driver running away on fire.

"This truck was passing by ... when it was hit by the heat wave and I saw the driver ablaze, getting off and walking away," he said.