Italian financial police have issued arrest warrants against six executives as part of an investigation stemming from the Genoa bridge collapse.
The six suspects are current and former managers of Italy's main private highway operator, Autostrade SpA.
Former CEO Giovanni Castelluci, maintenance director Michele Donferri Mitelli and operations manager Paolo Berti were placed under house arrest, while three managers still working for the company face restrictive measures.
The six suspects are being investigated for safety lapses and public contract fraud.
43 people were killed when the Morandi bridge collapsed during a rainstorm on 14 August 2018.
According to financial police, documents have emerged indicating that the six were aware that defective highway barriers had been installed in some parts of the company's vast highway network.
The executives are alleged to have resisted taking action to substitute the defective barriers or otherwise ensure their safety.
Autostrade said that work had been carried out on the barriers after the company became aware of an investigation last December.
"All of these barriers have already been checked and secured with appropriate technical interventions between the end of 2019 and January 2020, as part of the general infrastructure assessment carried out by the company on the entire motorway network," they said in a statement.
The integrated anti-noise barriers in question were present on around 60 of Autostrade's 3,000 kilometre network.
"All control and safety procedures, as well as design solutions for the replacement of barriers, have been defined with the relevant technical bodies of the Ministry of Infrastructure and Transport".
"Autostrade will evaluate all further interventions for its own protection based on the results of the investigation. "
The company said the six arrested individuals include four former ASPI managers and two technicians for the Genoa section and Mont Blanc Tunnel.
Autostrade, and its controlling company Atlantia, added one of the six suspects had already left the company and the two technicians have been suspended.
The cost of the operation to replace the barriers was estimated at around €170 million.
Atlantia, itself controlled by the Benetton family, has agreed to exit the company that manages the majority of Italy's toll roads and bridges, but terms are still negotiated.
The deal avoids the possibility that the government would remove Autostrade's concessions to run toll highways and bridges throughout the country.
A replacement bridge was opened in Genoa in August with much fanfare but relatives of victims refused to attend the inauguration ceremony.