Rescuers work amidst the rubble of collapses houses in Viareggio, Italy, on Tuesday. A rail car filled with liquefied natural gas exploded when a freight train derailed in the middle of the small town, setting off an inferno. (Fabrizio Giovannozzi/Associated Press)Rescue teams are searching for survivors after a freight train derailed in the middle of the night in northern Italy, setting off an explosion and fire that killed at least 14 people.

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

A train car filled with liquefied natural gas exploded, setting fire to a vast area. Witnesses described a white cloud followed by an explosion, smoke and flames.

Several homes and buildings collapsed or burned, killing some residents as they slept.

The death toll varied throughout the day, but civil protection officials put the official count at 14 dead and three missing after the body of a woman was found in her crumbled home. Some 35 of the 50 injured had suffered severe burns.

A firefighter sprays water on cars of a freight train that exploded outside the station in Viareggio. (Gregorio Borgia/Associated Press)

Assessment teams specializing in nuclear, biological and chemical threats are at the scene working to prevent other gas tanks at the scene from exploding.

Roughly 1,000 people have had to leave their homes as a precaution. Viareggio Mayor Luca Lunardini said hotel rooms and tents have been made available.

Severe burns

Officials said the fire was contained after several hours, but a smell of burning hung in the air.

"There are dozens and dozens of cars hit by the shock wave and collapsed houses," said firefighter spokesman Luca Cari.

Some of the victims, including a child, were killed in their homes, said Raffaele Gargiulo, a police spokesman for the nearby city of Lucca, which is in charge of Viareggio.

Two drivers on the road alongside the tracks were also killed.

The train's two engineers were only lightly injured. The derailing may have been caused by damage to the tracks or by a problem with the train's braking system, said Gargiulo.

With files from The Associated Press