MILAN (Reuters) - Three employees of companies owned by infrastructure group Atlantia were placed under house arrest on Friday, police said, as part of an investigation into the safety of motorway viaducts following the collapse of a bridge in Genoa.

The collapse of the Genoa viaduct in August last year killed 43 people.

The tax police, in a statement, said they had found evidence that safety reports for some viaducts had been falsified or information had been omitted with the aim of misleading transport ministry inspectors and avoiding further checks.

The three people placed under house arrest are employed by Atlantia’s motorway unit Autostrade per l’Italia and maintenance company SPEA Engineering.

Six other people at the same companies were temporarily banned from holding office, the police said on Friday, adding that the offices of the people targeted by the probe had been searched.

Shares in Atlantia quickly fell more than 7% in Milan on news of the house arrests, prompting them to be briefly suspended from trade.

A Milan trader said the arrests had revived concerns that the government could make good on a threat of revoking the company’s motorway concession.

The shares resumed trade and were down 6.6% down by 1138 GMT.

Atlantia and the two units have been under scrutiny since the collapse of the Genoa viaduct.

Around 70 employees at Atlantia and the transport ministry are already under investigation in a separate probe into the causes of the disaster.

Atlantia has always denied any wrongdoing.

Autostrade per l’Italia said in a statement that all the viaducts targeted by the investigation were safe, adding it had already moved the officials under house arrest to different jobs.

The company said it would consider possible legal action to protect its reputation.