The Italian public prosecutor's office has opened investigations into the managing director of the bus company whose vehicle was involved in an accident near Venice that left 21 people dead earlier this month.
Two city council officials responsible for bridge and road maintenance are also being investigated, the prosecutor's office said on Thursday, confirming earlier reports.
It remains unclear what caused the accident on October 3, when a tourist bus broke through a barrier, plunged 15 metres off a bridge and exploded in flames.
The vehicle had been carrying tourists from the historic centre of Venice to a campsite in nearby Marghera.
Thirteen injured people are still in hospital, with at least one of them struggling to survive.
A pair of German brothers, aged 4 and 13, were transferred to a hospital in Leipzig on Thursday, according to Italian authorities.
The investigation is currently partly focusing on the manager of the bus company La Linea, from which the campsite operators had chartered the vehicle. However, officials are also looking into the state of the bridge's safety protections.
An autopsy is currently being carried out on the driver, after initial speculation that he might have suffered a fainting spell.
