VIAREGGIO, Italy - At least 16 people were killed and 50 injured overnight in Italy when a freight train hauling liquefied petroleum gas derailed and exploded as it passed their homes, officials said Tuesday.

About 1,000 people were evacuated following the blast just before midnight Monday in the Tuscan seaside town of Viareggio, about 350 km (220 miles) north of Rome.

Thirty-seven people were serious injured, with 15 of them in critical condition, including a 2-year-old who was badly burned and was being transferred to a hospital in Florence, rescue workers said. Three children were among the dead.

It was Italy's most deadly rail accident since 17 people were killed in January 2005, when a passenger train collided with a freight train near the northern city of Bologna.

The emergency and danger are not over. The area has been sealed off and search and rescue operations are ongoing, said Guido Bertolaso, head of Italy's civil protection agency.

We have a convoy with four train wagons that are still carrying liquefied petroleum and are off the tracks, on their sides .... so the area is still at a really high risk level because the fire is still smoldering.

Firefighters battled overnight to contain blazes started by the explosion, which spread to nearby buildings and set cars alight. The area around the tracks was blackened and rescuers struggled to pull survivors from collapsed homes.

Viareggio Mayor Luca Lunardini said three or four people could still be buried under the rubble.

Pope Benedict said he shared the pain of Viareggio's residents and would pray for victims of the accident.

SAFETY STRIKE

GATX Rail Austria, a unit of the U.S.-based GATX Corp, which owns the rail cars -- each one consisting of a gas tank attached to a wagon -- said it did not know the cause of the explosion and was still collecting information.

So far we do not see any connection between the cause of the accident and our wagons, it said in a statement.

Railway workers will hold an hour-long strike across Tuscany Wednesday to demand for better rail safety. Their union said an axle on a wagon appeared to have buckled, making it derail.

Prime Minister Silvio Berlusconi called the episode serious and upsetting and was expected to visit the area Tuesday.

We were going to bed when my daughter smelled gas and we heard the blasts, said Roberta Marcelli. We looked out from the terrace and we saw windows exploding, everything was exploding.

State railways said the accident occurred when one carriage derailed, pulling another four with it. Liquefied petroleum gas escaped from a tank on one of the carriages and caught fire.
(Additional reporting by Phil Stewart, Gavin Jones and Silvia Ognibene; Writing by Phil Stewart; Editing by Sophie Hares)