Canadian National Railway locomotive engineers walked off the job at Midnight Friday after mediated contract talks collapsed.
Pickets were set up across northwestern Ontario including in the Rainy River district.
CN communications director, Mark Hallman, says supervisors and managers who are qualified engineers are taking over operation of the locomotives to minimize any possible disruption of freight service.
Teamsters union spokesman Stephane Lacroix says the dispute centres on CN's demands to limit a wage increase to 1.5 per cent and to revise mileage caps for the engineers.
With no further contract talks scheduled, the railway is pushing for binding arbitration to settle the dispute.
The union is offering to submit wage issues to binding arbitration on the conditional that all other outstanding issues are resolved at the bargaining table.
Meantime, a senior government official says Ottawa is prepared to table back-to-work legislation today to end the strike if the two sides haven't reached an agreement.
The official, who declined to be named, said the government would prefer the union and the company to negotiate but to protect the Canadian economy it could not let the strike continue.