Shares in Italian infrastructure group Atlantia, which operates the motorway on which a bridge in Genoa collapsed, were initially suspended on the Milan stock exchange today, but plunged more than 24 per cent when trading resumed an hour later.
Its shares had already closed 5.4 per cent lower on Tuesday.
Milan had been closed for a public holiday yesterday.
But when Atlantia shares re-opened after an hour's delay today, they were down 24.4 per cent at 17.79 euros after the government suggested that it could revoke Autostrade's operating licence for the motorway.
Deputy prime minister Luigi Di Maio charged yesterday that the tragedy "could have been avoided" and that it was clear that Autostrade per l'Italia was at fault for not carrying out maintenance.
The Italian government said it intended to fine the firm 150 million euros and cancel its concession.
The transport ministry told AFP it would first look at whether it was justified to revoke the concession for the A10 motorway and then look at all the other concessions.
"We'll let the investigators do their job, but we can't wait for criminal justice," said Prime Minister Giuseppe Conte.
"Our obligation is to ensure that everyone can travel safely. So, we will revoke the licence because there is no doubt... that Autostrade had the duty, the obligation and the commitment to ensure the maintenance of this viaduct and the safety of all those who travelled on it," he said.
In a statement today, Atlantia said that the decision to revoke its licence had been taken unilaterally.
"The announcement was publicly communicated lacking a specific default notice and without any verification of the material causes of the accident," it said.
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