Autostrade per l’Italia, controlled by infrastructure group Atlantia, manages the section of the A10 motorway linking the French border to the port city where the 50-year-old bridge gave way last Tuesday, killing at least 43 people.

Stefano Della Torre, head of the Department of Architecture, Built Environment and Construction Engineering at Milan’s Politecnico university, told Reuters the study flagged an “anomaly” in some of the stays that held up the bridge.

“The study highlighted an anomaly and recommended investigating the matter further,” he said in a phone interview.

Atlantia did not respond to a written request for comment and attempts to phone a company official were not successful.

The existence of the study was revealed by Italian newspapers on Friday.

Della Torre said the department’s staff had studied during the course of two nights in October how the bridge reacted to vibration and found an anomaly with some of the stays.

“The study flagged that there was an anomaly because elements which should have been reacting in the same way did not [do so],” he said.

Autostrade has said it monitored the bridge on a quarterly basis as required by law and that it had carried out additional checks by hiring external experts.

It also planned to strengthen the stays of the bridge and in April announced a 20-million-euro tender to award the works, a document on its website showed.

Della Torre said the study was commissioned to help assess the extent of the reinforcement needed.

Autostrade has come under fire over the disaster, with the Rome government threatening to withdraw the operator’s concession and calling for its top managers to resign. 

The company has said it will do everything possible to help establish the causes of the bridge collapse, which are being investigated by prosecutors in Genoa.

The bridge had presented problems since soon after it was completed in 1967, experts have said, and some of the stays were reinforced as early as the mid-1990s.

“We flagged what had emerged based on the type of investigation we conducted,” Della Torre said.

“But a more in-depth analysis was needed to better understand the matter and its seriousness. This was beyond our mandate.”

One of the peculiarities of the bridge was that metal rods of the stays were wrapped in concrete, making it hard to assess their condition.