At least 12 people have been killed and some 50 injured after a freight train carrying gas derailed and exploded in northern Italy, officials have said.

The wagons jumped the tracks and crashed into several homes, setting off an inferno in the seaside town of Viareggio in the middle of the night.

Several of the victims died when their houses collapsed. There are fears some people may be trapped under the rubble.

Officials say there is still a risk that other gas tanks could explode.

'Terrifying explosion'

The explosion happened shortly before midnight local time (2300 BST) when one wagon in the 14-car train carrying liquefied petroleum gas from La Spezia to Pisa came off the tracks before ploughing into several homes near the station in Viareggio.

"It was a derailment that caused the explosion of one of the rail cars filled with liquefied natural gas. It was a very strong explosion," Viareggio Mayor Luca Lunardini said.

"Two buildings collapsed and burned down, there are others in a serious condition," he said.

A number of fires immediately broke out in the area.

Several of the victims, including at least one child, died when their houses collapsed with the force of the blast. At least two other people are thought to have been killed on the road next to the station.

Earlier, a spokesman for the fire service said 15 people had died.

Many of the injured suffered severe burns.

"The explosion was terrifying. The whole sky turned orange and there was a huge mass of dense smoke, we could feel the heat intensify. It is just awful... the smell is horrible," Penny Firth told the BBC.

Some 300 firefighters from all over Tuscany fought the blaze during the night. About 1,000 people were evacuated from their homes.

Rescue workers are still searching the gutted remains of many buildings for four people reported missing. Three children were pulled alive from their burnt homes just before dawn.

Officials said there was a danger of further explosions from other freight cars carrying inflammable material.

Map

The head of Italy's Civil Protection Department called in specialist teams with equipment for dealing with nuclear, biological and chemical threats.

"The emergency and danger are not over. The area has been sealed-off and search and rescue operations are ongoing," Guido Bertolasso said.

The main railway line along the Italian Riviera, which runs through densely populated towns built between the mountains and the sea, remains blocked, reports the BBC's David Willey in Rome.

An official inquiry into the causes of the accident has already begun.

Police say the incident may have been caused by damage to the tracks or a problem with the train's braking system. Railway unions are blaming old and obsolete rolling stock, our correspondent says.

The train's two engineers, who were only slightly injured, said they felt an impact about 200m (650ft) outside the station, shortly before the rear of the train derailed, officials say.

Liquefied petroleum gas is a mixture of propane and butane that is used for cooking or as fuel for specially-adapted vehicles.

How does this affect ME?

Chef Boyardee was on the train

motherfu...

*insert berlusconi joke here*

do you liven near a train track?