A tanker truck carrying a highly flammable gas exploded after crashing into a truck on a crowded motorway in the northern Italian city of Bologna, killing at least two people.
Police said the accident and subsequent blast injured up to 70 people, some with severe burns.
Part of the raised motorway collapsed in the fireball, closing down a key route between northern Italy and the Adriatic Coast and other points south, including Florence and the capital, Rome.
Footage of the crash showed the tanker slamming into the back of a truck which had stopped in traffic.
The tanker immediately caught fire and another truck appeared to hit the tanker from behind.
After an unspecified amount of time, during which the motorway was cleared of most other vehicles, the truck exploded, causing part of the bridge to collapse and sending a fireball across eight lanes of the motorway and beyond.
The flames were followed by a thick cloud of black smoke and aerial photos showed a gaping hole left in the raised motorway.
The fire also spread to a car dealership beneath the bridge and several other vehicles burst into blames.
“The shockwave from the blast was extremely violent. Many of the injured received cuts from flying glass, which had shattered,” said Giovanni Carella, the emergency coordinator for the local fire service.
Italian prosecutors said the tanker was filled with liquid petroleum gas, otherwise known as propane, which is used as a fuel in heaters, cooking equipment and vehicles.