An engineering study commissioned by Italian highway operator Autostrade last year warned about the state of the concrete-encased cable stays that held up a bridge that collapsed this week in Genoa, two Italian newspapers reported on Friday.
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 bridge gave way on Tuesday, killing at least 38 people.
The bridge had presented problems since soon after it was completed in 1967 and some of the stays were reinforced as early as the 1990s, experts have said.
Atlantia had no immediate comment on the reports in La Stampa and Repubblica newspapers, which cited a study by engineers at Milan's Politecnico university in November 2017.
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.
The newspaper reports said the university study had found that the stays of the section of the bridge that later collapsed reacted to vibration "in a way that does not entirely conform with expectations and requires further investigation."
The study said the anomaly in the stays' reaction may have been linked to corrosion of metal in some cables.
One of the peculiarities of the bridge was that its cables were wrapped in concrete, making it hard to assess their state.
The newspapers said the company announced a 20 million euro ($23 million) tender in May this year as it planned to strengthen the stays that had not been reinforced in the 1990s.