At least two people are dead and dozens injured after a truck collision on an Italian highway sparked a massive explosion on Tuesday morning (AEST).

Italian media said a tanker containing inflammable materials collided with another truck on a bridge on the outskirts of the city of Bologna.

Part of the bridge collapsed and the resulting explosion and fire spread to a carpark below, where dozens of other vehicles caught fire and exploded.

Authorities said as many as 70 people were injured in the blast. Given the size of the explosion, they feared the death toll could rise.

A video shot from a parked car at the moment of the explosion appeared to show the two trucks bursting into flames almost immediately, before triggering a massive fireball that engulfs most of the surrounding vehicles.

#bologna #BorgoPanigale Le immagini della dinamica del grave incidente che ha coinvolto anche un mezzo che trasportava sostanze infiammabili. Indagini in corso #PoliziaStradale pic.twitter.com/aS8NKxTaoA

— Polizia di Stato (@poliziadistato) August 6, 2018

Police said they closed off the road where the crash took place as well as the surrounding area in Borgo Panigale.

Many of the injured were hit by debris and broken glass from the explosion, Italian media reported.

Marco Granna, a spokesman for the local health agency in Bologna, told CNN that 55 people were taken to hospital for treatment for burns.

Italian prosecutors told the Associated Press the tanker was filled with liquefied petroleum gas.

Firefighters said the extreme heat of the flames caused the raised roadway to collapse.

The windows of many houses in the area were also said to have shattered.

The blast caused part of the bridge to collapse, incinerating cars parked below. Photo: Twitter

Local police said the force of the explosion blew out windows at its barracks, injuring some officers with flying glass.

A woman living about a kilometre from the blast site said the explosion caused panic and confusion.

“I was in the house and I heard a huge bang and screams from the window. I saw a huge plume of smoke,” Crisina Felicani told local broadcaster Sky TG24.

“There was panic in the neighbourhood, because it wasn’t clear what happened.”

Many people were evacuated from the area due to thick black smoke, but also to allow firefighters to check nearby buildings affected by the blast to ensure they were safe to enter.

“It almost would have been an ordinary accident except for the highly flammable material this truck was transporting,” firefighter Carlo Cardinali told Sky TG24.

-with agencies