A year-long state of emergency has been declared after at least 39 people died in the collapse of a major bridge in Italy.

Fifteen people are injured and at least seven victims have pulled out of the rubble alive.

Italian Prime Minister Giuseppe Conte declared the 12-month state of emergency as the 10,000-strong rescue team, which includes 400 firefighters, continues to work at the scene in Genoa.

A fear the remaining structure may collapse has led to the evacuation of some 630 people who live near the Morandi Bridge.

Italian prosecutors do not believe the tragedy was an accident.

They are focusing their investigation on possible design flaws or inadequate maintenance.

Genoa prosecutor Francesco Cozzi told reporters: "I don't know if there is responsibility. For sure it was not an accident." 

Italy's transport minister earlier called for the top management of Autostrade per L'Italia, who managed the bridge, to quit and said its concession should be revoked.

The firm has said the CEO and chairman are not intending to resign at this stage.

The middle of the 51-year-old bridge collapsed during a violent storm on Tuesday.

More than 30 cars and three trucks fell 150ft as the road disappeared beneath them.

A worker inspects the the area around the collapsed Morandi highway bridge in Genoa Italy | Image: Nicola Marfisi/AP/Press Association Images

The number of vehicles - and victims - could have been much higher, had it not been for reduced traffic. Tuesday was the eve of Italy's biggest summer holiday.

Interior minister Matteo Salvini said three children - aged 8, 12 and 13 - were among the dead.

An unknown number of people are still missing.

Among the dead are a family of three who had been on holiday.

Ersilia Piccinino, her husband Roberto Robbiano and seven-year-old Samuele are believed to have died when their car fell to the ground.

Italian media reported that Samuele's toys, including a Spiderman football, were found inside the wreckage of the family's car.

Four of the victims are French, with three of them confirmed as young festival goers from Toulouse.

Two Albanians are also among the dead, as are three Chileans who live in Italy.

On Wednesday, Italian officials released the names of 21 citizens whose identities have been confirmed and families informed. Their ages range from eight to 68.

Image: Luca Zennaro/AP/Press Association Images

As well as managing the rescue efforts, two additional pressing issues facing those working to deal with the collapse are the fear that gas pipes in the area may begin to leak following the impact and that the flood-prone city may have a new crisis if the debris isn't cleared soon.

The piles of rubble and huge sections of road lying in the dry riverbed could become a dam in a matter of hours if heavy rains hit the Mediterranean port city of 600,000.

The 1967 bridge was considered innovative at the time for its use of concrete around its cables but was long due for an upgrade. It was servicing more traffic than its designers had envisioned.

Work to upgrade the bridge with a €20m project had already been approved.

Despite this, prosecutor Mr Cozzi indicated that no serious safety concerns had reached his office before the collapse on Tuesday, saying: "None of us would have driven over that highway 20 times a month as we do."