THE Italian engineer who designed the Genoa bridge that collapsed, killing dozens of people, warned four decades ago that it would require constant maintenance to remove rust given the effects of corrosion from sea air and pollution.

It comes as rescue workers found the bodies of three members of a family in the wreckage of Genoa’s collapsed motorway bridge, the last people reported missing in the disaster and bringing the death toll to 43.

RAI state television broadcast excerpts on Sunday of the report that engineer Riccardo Morandi penned in 1979, 12 years after the bridge bearing his name was inaugurated in Genoa.

At the time, Mr Morandi said there was already a “well-known loss of superficial chemical resistance of the concrete” because of sea air and pollution from a nearby steel plant.

Mr Morandi reaffirmed the soundness of the bridge design but warned: “Sooner or later, maybe in a few years, it will be necessary to resort to a treatment consisting of the removal of all traces of rust.”

Italy is searching for answers on Sunday after paying its respects to the dozens killed by the collapsed bridge.

The death toll from the disaster rose to 43 on Sunday after emergency services discovered three bodies, reported to be those of a couple and their nine-year-old daughter, overnight inside a car extracted from the rubble of the viaduct.

“The bodies of the final three missing people were found overnight,” Italy’s fire service said on Twitter Sunday.

“The fire service is continuing its inspection of the area in order to rule out the eventual presence of people not reported missing.”

The findings mean that all those reported missing after Tuesday’s tragedy have now been accounted for, although rescuers are continuing to comb the wreckage. Two of the nine injured still in hospital are in a serious condition.

The announcement followed the discovery on Saturday of the body of a labourer in his 30s in the rubble and the death of another man in hospital.

The disaster has caused public outrage and unleashed a fierce debate over the state of Italy’s infrastructure.

Rome has blamed the collapse on Autostrade per l’Italia, which manages almost half of the country’s highway network including the stricken A10 road that included the bridge.

But Giovanni Toti, president of the Liguria region where Genoa is located, asked that the government concentrate on drafting an “emergency law” for Genoa “that will allow us to work in a speedy fashion” rather than the battle with Autostrade.

The prosecutor investigating the bridge collapse has criticised past management of Italy’s infrastructure.

Francesco Cozzi said the state had “abdicated” its responsibility to ensure road safety by handing motorway management to the private sector, in an interview published Sunday.

“The philosophy of our system today sees a state stripped of its powers, a sort of absent owner,” he told the Corriere Della Sera newspaper.

Meanwhile, Mr Toti said that the hundreds evacuated from homes near or even under what remains of the bridge would be given new housing “within eight weeks”.

“We are working day and night to find comfortable accommodation for everyone,” he wrote on Twitter on Sunday.

“Work will begin this week. Within eight weeks maximum there will be a home for everyone. No-one should be left behind.”

Italy bid farewell to the victims, including several children, in Saturday’s solemn funeral that was boycotted by a majority of the families, who resented the presence of politicians and derided the ceremony as “a farce”.

Thousands of mourners packed into a flower-filled makeshift chapel where the coffins of 19 victims had been lined up.

An imam led prayers for two Muslim victims — a poignant gesture in a staunchly Catholic country where the far-right is now in power and which has seen a rise in attacks on foreigners.

Shortly after the official ceremony, Autostrade announced it would make 500 million euros ($A780 million) available to help those affected by the tragedy and rebuild the partially collapsed bridge.

The Morandi viaduct dates from the 1960s and has been riddled with structural problems for decades, leading to expensive maintenance and criticism from engineering experts.

The company’s boss Giovanni Castellucci said it would take eight months to build a new steel bridge in place of what was left of the viaduct.

But co-deputy prime ministers Luigi Di Maio and Matteo Salvini rejected the offer as insufficient.

The government plans to strip Autostrade of all of its lucrative contracts, which total 3,020 kilometres of Italy’s 7,000km-long motorway network.

The tragedy has shaken the whole country with key landmarks like Rome’s Colosseum switching off their lights in a sign of respect.