Firefighters work on the site of a bus accident on October 3, 2023 in Mestre, near Venice.
CNN  — 

At least 21 people were killed, including two children, when a passenger bus plunged from a bridge in Mestre, Italy, near Venice on Tuesday, in what has been described as an “apocalyptic scene.”

The bus was traveling from Venice to nearby Marghera and was “full of people returning home from work,” Venice mayor Luigi Brugnaro told state media RAI.

“It completely went off the road, it flew off the bridge. It was a bus; it was a highway. We are in mourning,” he added. Brugnaro described the scene as “apocalyptic” in a post on Facebook.

Francesco Martino, chief of staff of the prefecture of Venice, told CNN that 18 people were also injured in the crash and that authorities were still trying to determine what caused it.

The accident occurred on the overpass of a road that leads from Mestre to Marghera and the A4 motorway, Italian media skytg24 reported.

Children are believed to be among the victims of the crash.

For reasons that have yet to be determined, the bus broke through a wall of the overpass, falling between a warehouse and the tracks of the Mestre station below, according to skytg24.

“Following the impact, the vehicle caught fire,” the fire brigade wrote on X, formerly known as Twitter.

Morris Ceron, general director of the municipality of Venice, told the Italian public broadcaster RAI that the vehicle was headed towards a campsite.

“The identification of the bodies is underway,” Ceron told RAI.

Among the injured are Ukrainian, French, Croatian and German nationals, Venice prefect Michele Di Bari told RAI.

‘Tragedy of enormous proportions’

As authorities try and determine the cause of the deadly accident, RAI reported that the 40-year-old bus driver, identified as Alberto Rizzotto, was among the dead. The traffic counselor, Renato Boraso, told RAI that Rizzotto was an expert and had up to 7 years experience as a bus driver.

Luca Zaia, president of Italy’s Veneto region, called the bus crash in northern Italy, “a tragedy of enormous proportions.”

He said the accident involved some minors and “the victims and injured are of various nationalities, not just Italians.”

More than 20 ambulances “were used and the Treviso air ambulance was also called to the scene,” he said, adding that the injured were taken to hospitals in “Mestre, Mirano, Padua and Treviso.”

Images from the scene showed rescue workers by an overturned and crumpled bus below a bridge.

Rescue operations began at 7:45 p.m. local time (1:45 p.m. ET) and ended around 9:30 p.m local, according to officials.

The country’s president and prime minister expressed their condolences in the aftermath of the accident as did other world leaders.

“I express my personal and the Government’s deepest condolences for the serious accident that occurred in Mestre. Our thoughts go out to the victims and their family and friends,” Italian Prime Minister Giorgia Meloni wrote on X.

French President Emmanuel Macron said “thoughts this evening are with the Italian people, with the families and loved ones of the victims of the terrible tragedy in Venice” in a post on X.

“I am deeply saddened by the terrible accident of a bus in Mestre this evening. I offer my deepest condolences to the families and loved ones of the victims at this sad time. I’m close to you,” President of the European Council, Charles Michel, wrote on X.