At least 26 people were killed and 16 injured after a bridge collapsed in Genoa, Italy.

Italian Prime Minister Giuseppe Conte called it “an immense tragedy … inconceivable in a modern system like ours, a modern country”.

The disaster, on a major interchange connecting Genoa and other northern cities with beaches in eastern Liguria into France, focused attention on Italy’s ageing infrastructure, particularly its concrete bridges and viaducts built in the post-war boom of the 1950s and 1960s.

A truck at the bridge edge
A truck stopped right at the edge of the area where the Morandi bridge collapsed (Vigili Del Fuoco/AP)

What caused the Morandi Bridge to fall remains unknown, and prosecutors said they were opening an investigation but had not identified any targets.

Transport minister Danilo Toninelli said the collapse was “unacceptable” and that if negligence played a role “whoever made a mistake must pay”.

Early speculation focused on the structural weakness of the span.

Witnesses reported hearing a roar as the 45-metre bridge collapsed in torrential rain during midday traffic on the eve of a major holiday that sees most Italians abandoning cities for beaches and mountains.

Rescuers at work
Rescuers work in the debris (AP)

One unidentified woman who was standing below told RAI state TV that it crumbled as if it were a mound of baking flour. Video of the collapse, showing a misty scene of crumbled concrete, captured a man screaming: “Oh, God! Oh, God!”

Civil Protection authorities said at least 30 cars and three heavy vehicles were on the 80-metre section of the bridge that collapsed in the industrial area of warehouses.

There was an immense gap where the bridge used to be, and one heart-stopping image showed a green truck halted on the road just short of the edge.

The Morandi Bridge
The bridge would have been busy with holiday traffic on the eve of a major festival (AP)

More than 300 rescue workers and canine crews were on the scene. They used heavy equipment and dogs to search for survivors in the rubble. At least four people were pulled alive from vehicles under the bridge, ANSA reported.

“Operations are ongoing to extract people imprisoned below parts of the bridge and twisted metal,” said Angelo Borrelli, the head of Italy’s civil protection agency.

After visiting the scene, Mr Conte called the tragedy “a serious wound for Genoa, Liguria and Italy”.

An injured man
Several people were injured in the disaster (AP)

The Italian CNR civil engineering society said that structures dating from when the Morandi Bridge was built had surpassed their lifespan. It called for a “Marshall Plan” to repair or replace tens of thousands of bridges and viaducts built in the 1950s and 1960s.

Updating and reinforcing the bridges would be more expensive than destroying and rebuilding them with technology that could last a century.

They cited previous accidents: a bridge that fell in April 2017 in the northern province of Cuneo, crushing a carabinieri police car after the officers and driver had barely managed to get away in time; and an overpass that in the northern city of Lecco that collapsed under exceptional weight, crushing a car and killing the driver.