As many as 10-20 people may still be missing since a viaduct collapsed in the northwestern city of Genoa two days ago, local media cited the city's chief prosecutor as saying on Thursday.

"I cited data from rescue sources on site," Genoa Chief Prosecutor Francesco Cozzi told Sky TG24 private broadcaster in an interview.

He said the number was based on reports from relatives who have been unable to reach their loved ones since the bridge gave way shortly before noon on Aug. 14, plus estimates that about 30 cars and a few trucks were crossing it at the time of the collapse.

Regional and national authorities put the death toll at 39, with over a dozen injured.

"We worked through the night. Urban Search and Rescue (USAR) and canine units continue operations in the difficult search for survivors," the firefighter corps tweeted Thursday, along with video footage of rescuers and cranes digging through mountains of mangled concrete and metal.