VENICE — At least 21 people, including two children and foreign tourists, were killed on Tuesday (Oct 3) and several others wounded when a bus running on methane plunged off a bridge in Venice and caught fire.

Numerous others were injured in the crash on Tuesday evening.

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

The methane-powered bus was returning from Venice's historic centre to a camping site when the accident occurred around 7.30pm local time (1.30am on Wednesday, Singapore time).

Firefighters said it caught fire after careering off a bridge straddling a railway line and linking the Mestre and Marghera districts of Venice in northern Italy.

"A tragedy has struck our community this evening," Mayor Luigi Brugnaro wrote on Facebook, describing the crash site as "an apocalyptic scene".

Mr Luca Zaia, the governor of the Venice region, confirmed at least 21 dead and numerous others injured, some seriously, deploring a "tragedy of enormous proportions".

A city hall official said the dead included Ukrainian tourists while Italian news agency ANSA said the fatalities included German and French citizens. 

Three Ukrainians, a Croatian, German and French national were among the injured, a city official told AFP. 

Emergency workers spent hours removing the bodies, working overnight on the charred remains of the vehicle, which they finally removed from the scene in the early hours of Wednesday morning.

Mr Luongo, the fire chief, said the cause of the crash was not known, but "in the impact the electric batteries of the bus caught fire".

There was speculation that the driver, who was among the dead, suffered a sudden illness that caused him to lose control of the bus.

Investigators are analysing surveillance cameras from the area as part of their investigation into what happened.

CONDOLENCES

Italian Prime Minister Giorgia Meloni expressed her "profound condolences". 

"I am in contact with Mayor Luigi Brugnaro and (Transport) Minister Matteo Salvini in order to follow the news of this tragedy," she said in a statement. 

Mr Salvini said the cause of the accident could be the driver suddenly taking sick or becoming unwell. 

According to the Corriere della Sera newspaper, the bus swerved off the bridge, smashing through the barrier, and fell near railway tracks about 30m below.

The newspaper said it caught fire after hitting some power lines.

Interior Minister Matteo Piantedosi said the "aggravating factor" was methane, and that the fire spread rapidly.

"I fear that the death toll will rise," he added.

Francesso Moraglia, the Patriarch of Venice, was at the site where he blessed the dead — covered with white shrouds on which bouquets of red flowers had been placed.

French President Emmanuel Macron and European Union chief Ursula von der Leyen offered their condolences. 

German Foreign Minister Annalena Baerbock said she was "deeply saddened by the terrible bus tragedy... In this night of grief, my thoughts are with the victims, their families and friends".

Meanwhile, a spokesperson for the German foreign affairs department told AFP its embassy in Rome was working with Italian authorities to verify whether German nationals were among the victims.

In July 2018, a bus carrying a group of some 50 holidaymakers back to Naples fell off a viaduct near the city killing 40 people in all.