21 dead, including 2 babies, after bus falls off overpass near Venice, Italy

A bus crash on Tuesday in Mestre, Italy, a suburb near Venice, left 21 dead, including two babies, and another 15 riders injured, according to officials.

Prosecutors are investigating whether the 40-year-old driver suddenly became ill before the coach plunged off an overpass and onto a highway, officials said Wednesday. Investigators are also looking into whether the bus was certified.

The bus was carrying passengers to a campsite in Marghera when the wreck occurred, police said on X, the platform formerly known as Twitter.

Many of the injured, who were rescued in an evacuation operation, were listed as code red, indicating they were in critical condition. Authorities initially said 18 people were injured, but on Wednesday the number was revised to 15.

The injured passengers were taken to five hospitals in Veneto, officials said.

Venice City Councillor Renato Boraso told reporters that some of the passengers aboard the electric bus suffered burns.

Veneto Gov. Luca Zaia said most of the passengers on the bus were foreign tourists, but it remained unclear Wednesday what countries they were from. There were no immediate reports of Americans being on the bus.

Venice Mayor Luigi Brugnaro declared a state of mourning through Friday for the "tragic accident that occurred in Mestre," ordering flags to be lowered to half-mast across the city "in memory of the numerous victims who were on the fallen bus," he said in a statement posted on X.

European Union Commission President Ursula von der Leyen offered her "condolences to the families of the victims and those injured in the serious accident in Mestre."

Italian President Sergio Mattarella also called the mayor of Venice "to express his condolences for the very serious tragedy of Mestre," the official account of the Italian president posted on X.

The accident impacted the local railway network, shutting it down for a time, though services were later restored, officials said. Traffic in the area was impacted, according to a post from the City of Venice.

ABC News' Will Gretsky and Jolie Lash contributed to this story.