A motorway bridge has collapsed in the northwest Italian city of Genoa and fire brigade sources say 35 people were believed killed as vehicles plummeted to the ground.
Dramatic video footage captured the moment of the disaster when one of the huge supporting towers crashed down during torrential rain.
Vehicles and debris fell 45m (148ft) on to rail tracks, buildings and a river.
Rescuers are trying to free people caught in crushed vehicles or rubble.
Fears that other parts of the bridge might fall have prompted the evacuation of buildings in the area, a rescuer told Italy’s Ansa news agency.
Interior Minister Matteo Salvini promised that anyone found to be responsible for the bridge collapse would be held to account.
“I have crossed that bridge hundreds of times,” he said. “Now, as an Italian citizen, I will do everything to get the names and surnames of the managers responsible, past and present, because it is unacceptable to die like that in Italy.”
A representative of the motorway’s operator, Autostrade, told Reuters news agency there had been “no reason to consider the bridge was dangerous”.
Shares in Atlantia, Autostrade’s parent company which runs much of the country’s motorways, fell 6.3% after news of the collapse.
Prime Minister Giuseppe Conte is due to visit the scene to support the search-and-rescue effort and show solidarity with the victims and their families, his office said.
It fell around 11:30 local time (09:30 GMT) during heavy rain. Police reported a violent cloudburst.
“We saw lightning strike the bridge,” eyewitness Pietro M all’Asa was quoted as saying by Ansa. “And we saw the bridge going down.”
Engineers say it is too early to determine the cause of the collapse but that lightning is unlikely to be the reason.
Another witness, unnamed, recalled: “We heard an incredible roar and first we thought it was thunder very close by.
“We live about 5km [three miles] from the bridge but we heard a crazy bang… We were very scared… Traffic went completely haywire and the city was paralysed.”
One image posted by the regional emergency services shows a truck perched at the end of the surviving bridge section immediately before the drop.
A child is among the dead, said the head of the civil defence agency, Angelo Borrelli.
Between 30 and 35 cars and three heavy vehicles were on the bridge at the time of the collapse, he said.
The full horror of the collapse could be seen in aerial video of the scene.
Patrick Villardry, a French firefighter who came from Nice to help the rescue effort, told AFP news agency the task was huge.
“The first victims have been evacuated and now we have to search under the wreckage of buildings, but there are thousands of tonnes of concrete,” he said.