MILAN (Reuters) - Shares in Italy's Atlantia ATL.MI and other toll road operators came under heavy pressure on Thursday after the government said it would look to revoke a motorway concession and tighten rules after a deadly bridge collapse.

Shares in Atlantia, whose Autostrade per l’Italia unit manages the motorway that collapsed in the Italian city of Genoa killing at least 38 people this week, failed to start trading.

They were indicated down more than 20 percent.

Shares in rivals SIAS SIS.MI fell 8 percent, ASTM ATMI.MI fell 7 percent.