THE death toll from the collapse of a highway bridge in the Italian city of Genoa that is already confirmed to have claimed 39 lives will certainly rise, a senior official said.

“Unfortunately, the toll will increase, that’s inevitable,” Interior Minister Matteo Salvini told reporters.

Searchers continued to comb through tonnes of jagged steel, concrete and dozens of vehicles that plunged as much as 45 metres into a dry river bed on Tuesday, the eve of Italy’s main summer holiday.

Mr Salvini declined to cite a number of the missing, saying that would be “supposition,” but separately Genoa Chief Prosecutor Francesco Cozzi told reporters there could be between 10 and 20 people still unaccounted for.

“The search and rescue operations will continue until we find all those people that are listed as missing,” Sonia Noci, a spokeswoman for Genoa firefighters, said.

Italy is planning a state funeral for the dead in the port city on Saturday, which will be marked as a day of national mourning.

The service will be held in a pavilion on the industrial city’s fair grounds and led by Genoa’s archbishop, Cardinal Angelo Bagnasco.

Italian President Sergio Mattarella has said the collapse is an “absurd” catastrophe that has stricken the entire nation.

At least six of the dead are foreigners — four French citizens and two Albanians.

Authorities say they don’t know how many vehicles were on the bridge when it collapsed in a violent rainstorm.

Mr Cozzi has said the investigation of the cause is focusing on possible inadequate maintenance of the 1967 Morandi Bridge or possible design flaws.

In an interview on Thursday, Mr Cozzi said that there was a video of the collapse. Outside experts will study the video to see if it might help determine the cause.

Since the cause is yet to be ascertained, there are “no suspects” at this point, the prosecutor said. But he said prosecutors are considering possible eventual charges that include multiple manslaughter.

Premier Giuseppe Conte says his government won’t wait until prosecutors finish investigating the collapse to withdraw the concession from the main private company that maintains Italy’s highways, Atlantia.

Mr Salvini on Thursday demanded that the company offer up to 500 million euros ($784 million) to help families and local government deal with the aftermath of the disaster.

“If we’ve put up five million euros, they should offer 500 million,” he told reporters.

“There needs to be an immediate, concrete and tangible signal for these families: they should put their hands on their hearts and in their wallets.”

The bridge links two heavily travelled highways, one leading to France, the other to Milan.

A 20 million-euro ($31 million) project to upgrade the bridge’s safety had already been approved, with public bids to be submitted by September.

According to business daily Il Sole, improvement work would have involved two weight- bearing columns that support the bridge — including one that collapsed on Tuesday.

The bridge, considered innovative when it opened in 1967 for its use of concrete around its cables, was long due for an upgrade, especially since it carried more traffic than its designers had envisioned.

Some architects have said the choice of encasing its cables in reinforced concrete was risky since it’s harder to detect corrosion of the metal cables inside.