If the strike isn’t resolved, “we will go to zero within a few days if not immediately,” John Zahary, Altex chief executive officer, said late Thursday.

The Western Canadian oil patch has grown increasingly reliant on rail to get crude, Canada’s biggest export, to refiners as far away as the U.S. Gulf Coast in recent years as pipelines filled to capacity. CN shipped 180,000 barrels a day of crude in September, making up more than half of Canada’s total crude-by-rail exports that month.

About 3,200 conductors and yard operators at Canadian National walked off the job Tuesday, snarling shipments.