A strike is underway at the Blue Water Bridge in Sarnia.
47 employees have walked off the job after failing to reach a tentative agreement with the Federal Bridge Corporation.
The workers include cleaners, toll collectors, maintenance and currency exchange employees, all represented by the Public Service Alliance of Canada.
The corporation accuses the union of bad faith bargaining but says contingency plans are in place to keep the bridge between Sarnia and Port Huron open and traffic moving.
The union is warning of traffic slowdowns.