Shippers scrambled to shift freight onto trucks on Thursday as a strike at Canada's biggest railroad, Canadian National Railway Co., entered its third day and left the critical fuel propane and other goods stranded.

Some 3,200 unionized employees, including conductors and yard workers, hit picket lines on Tuesday in the biggest such action in a decade. The strike over working conditions has slowed output at industrial plants making chemicals, canola oil and other products.

It has also held up deliveries of propane, used to heat homes in some provinces and to fuel crop dryers for farmers.