Twenty-one people have died and at least 15 were injured in a fiery bus crash in a borough of Venice, Italy, across the lagoon from its historic centre.

Firefighters and other emergency responders worked into the night trying to extract bodies and extinguish the flames.

The victims included at least four Ukrainians and a German citizen, according to Venice prefecture.

Injured people, including five in a serious condition, included French, Spanish and Croatian nationals, local officials said.

At least two of the dead were children, Venice prefect Michele Di Bari said, adding that many of the people involved in the accident were “young”.

The bus was carrying foreign tourists when it fell from an elevated street on Tuesday in Mestre en route to a camping site near the community of Marghera, a Venice official said.

The Italian driver, Alberto Rizzotto, was killed in the crash. Venice prosecutors are investigating if he felt ill while he was driving. He was an experienced driver, Venice city councillor Renato Boraso said.

Mauro Luongo, commander of the Venice firefighters team, said: “The people in the bus found themselves surrounded by flames.

“The scene we found was terrible. It took about one hour to extract some of the bodies.”

Venice mayor Luigi Brugnaro wrote on X, the social media platform formerly known as Twitter, that the crash scene was “apocalyptic” and declared the city in a state of mourning.

Four of the injured were in a serious condition following the accident, which happened on the mainland just 3.7 miles north-west of the old city of Venice, said Mr Boraso. Two of the dead were children, another official said.

The injured were transferred to five different hospitals in the region.

According to local media, the bus fell a few feet before crashing close to Mestre’s railway tracks, where it caught fire.

The Veneto region governor, Luca Zaia, told RAI state television that the cause of the accident was still unclear.

“This is an important tragedy, but it’s difficult to understand how it happened,” he said. “The bus was new and electric, and that street wasn’t particularly problematic.”

In 2017, 16 people on a bus carrying Hungarian students died in an accident near the northern city of Verona. And in 2013, 40 people were killed in one of Italy’s worst vehicle accidents when a bus plunged off a viaduct close to the southern city of Avellino.