Ian Firth, a structural engineer and specialist in bridges, said the Morandi bridge is of a "very unusual design".

“It is too early to say what caused the tragic collapse, but as this reinforced and pre-stressed concrete bridge has been there for 50 years, it is possible that corrosion of tendons or reinforcement may be a contributory factor," the former president of the Institution of Structural Engineers said.

He said the storm taking place at the time and the ongoing work on the foundations may or may not be relevant - we simply do not know yet.

The Morandi bridge stands on the A10 toll motorway, which serves the Italian Riviera and southern coast of France.

While part of it spans the Polcevera waterway, it is more than a kilometre long - with other portions reaching over railway lines and buildings.

The Morandi bridge was built in the 1960s, but restructuring work was done in 2016.

Reuters reports that the 1.2km-long bridge was undergoing further work to shore up its foundation at the time of collapse.

It quoted the highway operator as saying the bridge was "constantly monitored".

Italian journalist, Matteo Pucharelli, from La Repubblica newspaper, is at the scene of the accident.

"I'm under the bridge and there are 20, 30 cars. 200 people are helping the rescue - policemen, the ambulance, helicopter - and they are finding people in the river," he told the BBC.

Several people were injured when the bridge fell onto their homes near the bridge in Genoa.

Two people were seriously injured when the bridge collapse crushed their homes, Italian news agency Ansa reports.

An elderly woman suffered smoke inhalation injuries in a fire at her home near the bridge.

Hospital sources told the agency that a man in his 30s has a severe head injury.

Footage appears to show the moment a Genoa bridge collapses, sending vehicles falling to the ground.

The latest photos show firefighters searching under huge sections of collapsed masonry.

Image source, Reuters

Scores of firefighters are working to free those trapped in the debris caused by the bridge collapse.

The Italian fire brigade has shared footage of a helicopter flying over the bridge in rainy weather.

At least 22 people have been killed in the Morandi bridge collapse in the city of Genoa, Italian Deputy Transport Minister Edoardo Rixi said in a television interview.

"The central section (of the bridge) came down," Mr Rixi said on SkyNews24, speaking from Genoa.

He warned that the death toll will rise.

France is ready to send help to Italy, President Emmanuel Macron tweeted, expressing condolences for the victims.

Italy's Interior Minister, Matteo Salvini has thanked the "200 firefighters (and other heroes) at the scene".

Mr Salvini tweeted out pictures from the situation room, as the government co-ordinates its response to the bridge collapse.

"We are following the situation as it unfolds," he said.

The U.C. Sampdoria football team, which plays in the city, says it is "left speechless" by the disaster, in a Twitter post.

The Italian national team manager, Roberto Mancini, has expressed his condolences to the families of those killed and injured.

The former Manchester City manager made more than 400 appearances for Genoa's Sampdoria between 1982 and 1997.

The latest photographs show the huge length of bridge that fell - reported to be as much as 100m (330ft).

Image source, Reuters

Image source, Reuters

"We live about five kilometres (three miles) from the bridge, but we heard a big bang. At first, we thought it was thunder very close to us," a Genoa resident told the Ansa news agency.

"When we heard an incredible roar we were scared, very scared."

The Italian interior ministry say an infant child is among the dead, with a confirmed death toll of 11 at this time. Many of the injured have been taken to hospital.

An earlier image tweeted by firefighters showed this truck standing precariously on the stricken bridge.

This shot shows heavy rain lashing the bridge at the time.

Image source, EPA

Rescuers are now picking through dozens of crushed vehicles.

A witness quoted by Italy's Ansa news agency said a lightning strike hit the bridge just before the collapse.

Some heavy vehicles fell into the Polcevera stream when about 100m (328ft) of bridge collapsed, Ansa said.

Part of a warehouse was demolished when the bridge came down.

Video taken by a helicopter is circulating on Twitter, giving a different vantage point of the damage:

The bridge collapse has killed at least 11 people and seriously injured at least five, according to a preliminary assessment by the Italian interior ministry.

But there are fears that the death toll will rise to dozens.