The toll from Tuesday's gas train explosion in the Tuscan town of Viareggio rose to 19 Thursday as a woman died in hospital.
About ten of the burns patients from the disaster are fighting for their lives, hospitals said.
Italian Premier Silvio Berlusconi said the government was considering ''changing the rules for the transport of these tanker cars''.
He did not go into specifics, but promised a ''thoroughgoing'' investigation into the cause of the disaster.
Italian rail chief Mauro Moretti told parliament that the train derailed when a part, believed to have been a rusty axle, gave way.
He said wagon parts were originally made in the East Germany in 1974 but were passed fit for use in 2004.
Moretti denied reports that the axle showed signs of being soldered by rail safety workers.
''I've read some amazing things, written by people who are supposed to be experts...There was no soldering, it just gave way,'' Moretti said at a Senate hearing.
The derailed railcar was owned by a Vienna-based subsidiary of the US-based GATX Corp.
Moretti said Italian rail would not use GATX wagons until the firm provided information on their components.
GATX said it can see no connection between its wagons and the disaster but it is gathering information.
The Italian company which last checked the railcars, Cima, said it had fitted some replacement wheels from GATX in March.
A leading Italian consumer protection association, Codacons, said it would sue the Italian rail safety agency and was mulling class action against GATX in US courts.
Viareggio prosecutor Aldo Cicala said a probe had been opened into ''possible manslaughter by person or persons unknown''.
He said ''possible buckling' of a mechanical component' may have caused the disaster, Italy's worst since 17 people were killed at Bologna station in 2005.
''We can't say any more because the investigation is ongoing,'' Cicala said.
Five children are among the victims of the blast, which happened after a car carrying liquid gas derailed and a fireball engulfed buildings.
Sixteen of the 19 victims were so badly burned that it was initially possible only to identify three of the bodies.
But officials have now managed to identify ten of them.
