VENICE, Italy - At least 21 people died on Tuesday and 18 were injured after a bus carrying tourists to a campground crashed off an overpass near Venice in northern Italy and caught fire, city officials said.

Rescue personnel attend the scene, after a coach crashed off an overpass in Mestre, Italy, October 3, 2023. Photo: Reuters

The bus veered off the road and fell close to railway lines in the district of Mestre, which is connected to Venice by a bridge.

The cause of the accident was unclear. Venice city councillor Renato Boraso said one line of enquiry was that the driver, a 40-year-old Italian who was among those killed, had been taken ill before the crash.

"It's an appalling tragedy, the city is in mourning," Boraso told Sky Italia television.

He said the coach had been carrying 40 passengers, of whom 21 had died and 18 were injured. The death toll could rise because several of those hurt were in a critical condition, he added. Venice's city hall said the injured people had been taken to nearby hospitals, with four in a serious condition.

Firefighters and rescue personnel work near a coach after it crashed off an overpass in Mestre, Italy, October 3, 2023. Photo: Reuters

Rescue personnel work next bodies at the scene of a crashed bus, in Mestre, Italy, October 3, 2023. Photo: Reuters

Officials said the vehicle fell around 15 metres (50 feet) onto electricity lines and caught fire at around 7:45 pm local time.

"It's an apocalyptic scene. I am speechless," Venice's Mayor Luigi Brugnaro posted on X, formerly known as Twitter.

Five of the victims were Ukrainians and one was German, said Venice's prefect Michele Di Bari, the local representative of the interior ministry.

The bus was also carrying passengers from France and Croatia, Italian news agency ANSA reported.

"The bus is totally crushed. The firefighters had difficulty getting a lot of the bodies out," Di Bari told Sky Italia television. He said two children were among the victims.

Late on Tuesday evening, rescuers were still struggling to remove the wreckage of the bus to make sure no more passengers were trapped inside.

Prime Minister Giorgia Meloni expressed her condolences, saying in a statement that her government's thoughts were with "the victims, their families and their friends."

Firefighters works amid Fire brigade vehicles at the scene of a crashed bus, in Mestre, Italy, October 3, 2023. Photo: Reuters

Italy has suffered a number of deadly bus crashes in recent years.

In 2017, 16 people on board a bus carrying Hungarian students died in an accident near the northern city of Verona, while 40 people died in 2013 when a bus plunged off a viaduct in southern Italy.