GENOA, Italy — Firefighters continued a round-the-clock search of rubble in this north Italian city Wednesday as questions were raised about what caused a bridge collapse that killed at least 39 people.

Deputy Prime Minister Matteo Salvini warned that whoever was responsible would have to "pay dearly" after an 80-yard section of the Morandi Bridge in Genoa fell following a violent storm Tuesday.

Dozens of cars and three trucks plunged as much as 150 feet to the ground. Around 400 firefighters worked through the night, lifting chunks of concrete to create spaces for rescue teams to check for survivors.

Italian Transport Minister Danilo Toninelli said the government would inspect aging bridges and tunnels across the country to determine if a program of remedial works is required.

Corruption in the public sector has been highlighted as an issue in recent years.

A 2014 report by the European Commission warned that infrastructure projects were at the greatest risk of corruption and infiltration by organized crime as part of Italy's public procurement process.

Such corruption occurs most frequently at the stage when quality checks are carried out, according to experts.

Although Italy has taken steps to curb the issue, a study published last year described corruption in the country's infrastructure as "an elephant in the room" that can send costs soaring up to 50 percent over budget.

"The cost performance of Italian infrastructure is dramatically worse than elsewhere," it said.

Vehicles remained on the Morandi Bridge in Genoa on Wednesday. Luca Zennaro / AP

When the highway overpass was completed in 1967, it was considered innovative for its use of concrete around its cables.

However, traffic levels on it were higher than its designers had envisioned. One expert in such construction, Antonio Brencich at the University of Genoa, had previously called the bridge "a failure of engineering."