Separately, local officials say they are taking data from people whose friends or relatives are missing, but that they do not yet know how many cars exactly were on the bridge when it collapsed and can not extrapolate how many people might be buried in the rubble.
Nicola said people started shouting and waving their arms out of vehicle windows to tell people to reverse.
The bridge sees some 25 million vehicles every year, and a 2011 report by an Italian highways company said that the bridge had been suffering from degradation.
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Deputy Prime Minister Luigi Di Maio said on Wednesday that the tragedy "could have been avoided" if Autostrade per l'Italia had maintained the road properly.
Matteo Pierami drove across the bridge with his wife and child, aged two months, nearly an hour before it collapsed.
"Autostrade should have done maintenance and didn't do it", he alleged.
Transport Minister Danilo Toninelli called on Autostrade's leadership to resign, accusing the company of putting profits ahead of safety.
But Autostrade defended its overall safety record.
Responding to Interior Minister Matteo Salvini's appeal for the company to give the families of victims a concrete response, the company says "our apologies are in our words and deeds". He tweeted that those responsible will "pay dearly".
Genoa's chief prosecutor, Francesco Cozzi, said 10-20 people were still missing.
The incident, which occurred during a violent and sudden storm, sent around 20 cars and three heavy trucks tumbling as an 80-metre stretch of elevated highway fell away.
View of the buildings (top) that were evacuated in the area around the collapsed bridge on Wednesday.
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Sniffer dogs and large earth-movers are being used to search around large chunks of concrete in the debris of the collapsed bridge.
Coffins carrying the victims of the Genoa bridge collapse began to be laid out in a hospital chapel on Thursday (August 16) with grieving relatives huddled next to their loved ones.
Witness: "It has collapsed".
Italy's national fire service said on Twitter that 200 of its emergency workers were involved in the rescue effort.
The driver of a green lorry left precariously close to the edge told Italian media how he had escaped the "hell" of the bridge collapse.
Italian ministers have criticized the company in charge of managing the country's motorways after the Genoa bridge collapse on Tuesday that killed 39 people. Three French citizens and two Albanians were also killed.
He said that in the seven years from 2014 to 2020 Italy was set to receive 2.5 billion euros ($2.8 billion) for roads and trains, 12 billion euros in so-called structural funds to help poorer regions, and had been given the green light to receive 8.5 billion euros in national spending.
Pope Francis offered prayers for all those affected.
"I've had some time to calm down and am now trying to understand what happened, but my wife and our friends are very shocked", Pierami said.
Opened in 1967, the bridge is part of the A10 motorway connecting Genoa to France and is named after designer Riccardo Morandi. Restructuring work on the bridge was carried out in 2016.
"Even without this tragedy the likelihood of the Italian government testing the EU's patience with respect to its budget rules was always likely to be there", CMC Markets analyst Michael Hewson said.
"There are hundreds, thousands rather, of bridges at risk of collapse", he said, adding that the exact number is unknown and that the biggest problem is a lack of information about the 1.5 million or so bridges in Italy.
The disaster, on a major interchange connecting Genoa and other northern cities with beaches in eastern Liguria into France, focused attention on Italy's aging infrastructure, particularly its concrete bridges and viaducts built in the postwar boom of the 1950s and 1960s.