Serious questions are being raised about the state of repair of the Genoa bridge that collapsed, with the city council being told in 2012 it could fall down in 10 years.
The Genoa Public Prosecutor's Office blamed "human error" for the collapse that killed 39 people and injured 24.
The Office has opened an investigation into possible negligent homicide.
Italian prime minister Giuseppe Conte has also declared a 12-month state of emergency, saying he would make an initial €5m available to the region.
There has been anger and disbelief in Italy that such a vital structure could have simply given way.
The cause is not yet known but there has been heavy criticism of the private company responsible for operating the bridge.
Rescuers have said there is little hope of finding more survivors underneath the Morandi bridge, where dozens of vehicles fell from a height of 45m in Tuesday morning's collapse.
More than 400 people have been evacuated from the area. Residents of housing blocks under one pillar were ready to move back, but were then told it was cracking and that their homes were at risk.
Vehicles on the Morandi motorway bridge the day after a section collapsed in the north-western Italian city of Genoa. Photo: AFP
It's not yet clear what went wrong with the bridge.
There was torrential rainfall at the time, and a huge tower and sections of the bridge - measuring about 200m - collapsed on to railway lines, a river and a warehouse.
The motorway operator said work to shore up the bridge's foundation was being carried out at the time.
Autostrade per l'Italia said in 2011 the bridge had been suffering from degradation due to heavy traffic.
Were safety warnings ignored?
The state of the bridge and the responses to the collapse throw light on what has been a long-standing debate about Italian infrastructure.
This was the fifth bridge collapse in Italy in five years, according to Corriere Della Sera.
There have been previous reports and comments questioning how the Morandi bridge was built and how long it could last.
In December 2012, the Genoa city council discussed the state of the bridge at a public hearing into how to expand the local transport infrastructure. A local industry confederation official spoke of the collapse of the Morandi bridge "in 10 years".
In 2016, structural engineer Antonio Brencich spoke of "errors in this bridge".
The issue of transport in the area is now critical, given that the bridge was a major arterial route for an important port city.
The Morandi bridge, built in the 1960s, stands on the A10 toll motorway, an important conduit for goods traffic from local ports which also serves the Italian Riviera and south-east coast of France.
The prime minister has said all infrastructure across the country will be double-checked in the wake of the collapse.
A day of mourning
Italian Prime Minister Conte declared a 12-month state of emergency.
He also announced a national day of mourning would take place, which the government wanted "to coincide with the funerals of the victims".
"These are unacceptable tragedies that should not happen in a modern society. This government will do everything to prevent such tragedies from happening again."
Mr Conte confirmed the government's intention to revoke the contract from private sector firm Autostrade per l'Italia, which was in charge of operating and maintaining the bridge and the A10 motorway it was part of.
The highways firm defended its maintenance record, saying it had checked the bridge every three months using highly specialised techniques.
Who were the victims?
They included families in their cars, people going to work, and people going on holiday.
Most of them were Italians, but the French Foreign Ministry said four of its nationals had also died.
Among the dead were a family of three - Roberto Robbiano, 44, Ersilia Piccinino, 41, and their young son Samuel.
One of the most compelling testimonies came from Davide Capello, 33, a former goalkeeper for Serie A side Cagliari.
His car fell 30m in the collapse, but came to rest in a pocket between the columns and survived.
"I was able to get out... I don't know how my car wasn't crushed. It seemed like a scene from a film, it was the apocalypse," he said.
Valentina Galbusera, 43, a doctor, told La Stampa: "The bridge fell in front of me, not even 20m away, I avoided the collapse by only a couple of seconds. I felt the bridge was shaking and I tried to reverse. Then I got out of the car and started running."
- BBC
