A bridge over an industrial area in the Italian city of Genova partially collapsed during a sudden and violent storm on Tuesday, leaving vehicles crushed in the rubble below.
Italian media reported that there were deaths, but Maria Luisa Catalano, a police official in Genoa, said that authorities were still involved in rescue efforts and did not yet know the number of victims or injured.
The disaster occurred on a highway that connects Italy to France and other vacation resorts on the eve of a major Italian holiday on Wednesday, Ferragosto, and traffic would have been heavier than usual as many Italians travelled to beaches or mountains.
The transport minister, Danilo Toninelli, called the collapse "an enormous tragedy."
The private broadcaster Sky TG24 said that a 200-metre section of the Morandi Bridge collapsed over an industrial zone.
Firefighters told The Associated Press that there are concerns about gas lines.
Photos published by the ANSA news agency on its website showed a huge gulf between two sections of the bridge.
Video captured the sound of a man screaming: "Oh god, oh, god." Other images showed a green truck that had stopped just metres short of the gaping hole in the bridge.
Interior Minister Matteo Salvini said some 200 firefighters were responding to the accident. "We are following minute by minute the situation for the bridge collapse in Genoa," Salvini said on Twitter.
The Morandi Bridge was inaugurated in 1967. It is 90 metres high, just over a kilometre long, with the longest section between supports measuring 200 metres (yards).
The bridge is a main thoroughfare connecting the A10 highway that goes toward France and the A7 highway that continues north toward Milan.
ANSA said that authorities suspected that a structural weakness caused the collapse on Tuesday.