Italian rescuers searched through the night Wednesday for any survivors under the shattered remains of a motorway bridge in Genoa as investigators probed what could have caused such a catastrophic collapse.

Some 30 people were killed on Tuesday when a vast span of the Morandi bridge collapsed during a heavy rainstorm, sending vehicles and their drivers plunging 100-metres onto railway tracks below.

Rescuers spent the night searching the tangled remains of the bridge under floodlights and there are fears the toll could rise in what the Italian government has called an “immense tragedy”.

The collapse came as the bridge was undergoing maintenance work and as the Liguria region, where Genoa is situated, experienced torrential rainfall.

“Unfortunately there are around 30 dead and many injured in a serious condition,” Interior Minister Matteo Salvini told reporters.

Italian President Sergio Mattarella said a “catastrophe” had hit Genoa and the whole of Italy, as attention turned to what might have caused the collapse and who might be ultimately responsible.

“Italians have the right to modern and efficient infrastructure that accompanies them safely through their everyday lives,” Mattarella said in a statement.

Prime Minister Giuseppe Conte said “all infrastructure” across the country needed to be double-checked. “We must not allow another tragedy like this to happen again,” he added.

Rescuers scouring through the wreckage, strewn among shrubland and train tracks, said there were “dozens” of victims, as rescue helicopters winched survivors on stretchers from the ruined bridge.

Cars and trucks were tangled in the rubble and nearby buildings damaged by vast chunks of concrete, according to an AFP photographer at the scene.

“We’re not giving up hope, we have already saved a dozen people from under the rubble,” a fire official, Emanuele Giffi, told AFP.

“we are going to work round the clock until the last victim is secured.”

As cars and trucks tumbled off the bridge, Afifi Idriss, 39, a Morrocan lorry driver, just managed to come to a halt in time.

“I saw the green lorry in front of me stop and then reverse so I stopped too, locked the truck and ran,” he told AFP.

The green lorry was still on the bridge late evening, stopped just short of the now yawning gap.

The incident, the deadliest of its kind in Europe since 2001 is the latest in a string of bridge collapses in Italy, a country prone to damage from seismic activity but where infrastructure generally is showing the effects of a faltering economy.

Aerial footage showed more than 200 metres of the viaduct, known locally as the Morandi bridge, completely destroyed.

The cause of the disaster was not immediately clear, although weather services in the Liguria region had issued a storm warning Tuesday morning.

The national motorways body said on its website that “maintenance works were being carried out on the base of the viaduct”, adding that a crane had been moved on site to assist the work.