The death toll from Tuesday's gas train explosion in Viareggio rose to 17 Wednesday as two small children and a man died in hospital.
Transport Minister Altero Matteoli told parliament that 20 of the 31 people injured are in critical condition.
Two children, aged 2 and 3, suffering from burns on 90% of their bodies, died in hospital.
Four children have now died after a fireball engulfed homes and streets in the Tuscan seaside town early Tuesday.
Three people are still missing, Matteoli told parliament.
He gave the official toll as 16, including the children, but acknowledged there were reports of another death.
The minister said the part of the train which appeared to have broken ''showed signs of rusting''.
Matteoli said his ministry was examining the possibility of making a special examination of train tanker cars, used for the transport of liquid gas and other explosive fuels, which are registered abroad.
The minister denied accusations by some MPs that rail safety funds had suffered because of budget cuts.
In Viareggio, operations continued to empty gas from the other tanker cars involved in the train wreck.
The local police said no one had so far been placed under investigation for the disaster, which happened when a train derailed and spilled liquid gas into streets.
A spark ignited the gas, sending a sheet of flame down streets and into buildings where people were burned alive as they slept.
The cause of the accident has yet to be established but Italian railways CEO Mauro Moretti told Sky TV that an axle on one of the trucks appeared to have snapped.
Moretti said the axle was rusted and looked as if it had suffered progressive strain.
But he stressed that Italian railways were ''the safest in Europe''.
The rail CEO will be heard by the Senate Thursday.
Meanwhile rail workers cleared the track and removed the remaining liquid from the train.
Rail unions have suggested the accident was caused by old rolling stock.
But the company that owned the wagon, a Vienna-based subsidiary of US-based GATX Corp, said it was new.
Police in Viareggio are on the alert for possible looting from abandoned homes.
A young man carrying a baseball bat was arrested as he approached an empty building.
Premier Silvio Berlusconi, who visited the scene Tuesday, has cancelled a trip to an African Union summit to deal with the disaster.
He has declared a state of emergency and promised to cover 100% of the cost of rebuilding the homes.
Some 200 people were displaced by the disaster but most of them have found room among families and friends.
