Who was on the bus?

The passengers were thought to be mostly tourists on their way back from a visit to Venice’s historic centre.

Luca Zaia, the governor of the Venice region, confirmed on Wednesday morning the official death toll was 21, “including a one-year-old child and a teenager”.

Five Ukrainians were among the dead identified so far, alongside a German, a Croatian, a Frenchman and the Italian driver, he said.

READ ALSO: Venice mourns after 21 killed in tourist bus accident

The driver was named as 40-year-old Alberto Rizzotto from Treviso. His colleagues told Ansa of their “shock”, describing him as an expert driver who had been in the job for seven years.

Among the 15 injured being treated in hospital were German, Austrian, Ukrainian and Spanish nationals, reported Ansa, including German brothers aged 7 and 13 who had lost their parents in the crash.

Five of the injured were in a “very serious condition”, and some were still being identified, Zaia said.

Where was the bus travelling to and from?

The bus had been returning on Tuesday evening from Venice’s historic centre to a campsite on the mainland where the tourists were staying.

Corriere reported that the bus was “in service on behalf of the Hu campsite in Marghera.”

“The Human Company group, owner of Hu Venezia camping in town, which hosted some of the people involved in the accident that occurred this evening in Mestre, expresses its deepest condolences and maximum closeness to the families of the bus passengers,” the campsite’s owners said in a statement published by Italian media on Wednesday.

The company, which runs several accommodation facilities and other hospitality businesses around Italy, said it was in contact with “hospitals and the competent authorities for updates on the evolution of the situation and the condition of the injured.”

How did the accident happen?

Firefighters said the bus caught fire and then careered off the Rizzardi flyover, a road straddling a railway line and linking the Mestre and Marghera districts of the northern Italian city.

“The bus flipped upside down. The impact was terrible because it fell from over 10 metres,” Mauro Luongo, fire brigade commander of Venice, told reporters at the scene.

According to newspaper Corriere della Sera, the bus swerved off the bridge after smashing through the barrier and fell near railway tracks below.

Firefighters also said on Wednesday the bus was electric, despite the Italian interior minister earlier saying it ran on methane and that this had been an “aggravating factor”.

They spent hours extracting bodies from the charred remains of the bus, which was finally removed from the site in the early hours of Wednesday.

“Among the difficulties was the fact that the bus was electric so it had batteries. Unfortunately, they caught fire on impact,” said Luongo.

It remained unclear on Wednesday morning how the fire had started.

Firefighters said they had ruled out an earlier hypothesis that a fire had started on board the bus.

Zaia said, “the main hypothesis at the moment is that the bus driver… may have fallen ill.”

The driver was an employee of the Martini Bus company, which had rented the vehicle to another company called La Linea, Ansa reported.

“The bus was new and [the driver] was good,” Massimo Fiorese, CEO of La Linea, told Ansa.

What happens next?

The Venice Public Prosecutor’s Office had opened an investigation into the deaths, Ansa reported on Wednesday morning.

“At present we are not able to make a precise reconstruction of events”, stated prosecutor Bruno Cherchi, saying that his office would initially be working on “both ordinary checks and acquiring all the elements necessary for identification” of the passengers.

Statements from surviving passengers and analysis of video footage from surveillance cameras on the road and internal cameras on the bus would be key to this stage of the investigation, reports said.