MILAN — Italian financial police on Wednesday issued arrest warrants against six current and former managers of Italy's main private highway operator as part of investigations stemming from the Genoa bridge collapse that killed 43 people in August 2018.

Former CEO Giovanni Castelluci, maintenance director Michele Donferri Mitelli and operations manager Paolo Berti were placed under house arrest. While financial police said restrictive measures also applied to three current employees, Autostrade said one had already left the company and two have been suspended. All are investigated for safety lapses and public contract fraud.

According to financial police, documents have emerged indicating that the six were aware that defective highway sound barriers had been installed in some parts of the company's vast highway network, and resisted taking action to substitute them or otherwise ensure their safety.

Autostrade said in a statement that the barriers in question were installed on 60 kilometers (37 miles) of the company's 3,000-kilometer network, and that work has already been carried out to secure the barriers after the company became aware of an investigation last December.

Atlantia SpA, which controls Autostrade, saw its shares fall 2.8% at 15.08 euros ($17.76).

Atlantia, which is controlled by the Benetton family, has agreed to exit the company that manages most of Italy's toll roads and bridges, but terms are still being worked out. 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 with much fanfare this summer.