Police say the incident took place just before noon, about two kilometres east of the community of Hazelton, when the truck moved right on Highway 16 so two vehicles could pass.
As a result, the truck's right-side wheels caught the highway's soft shoulder and the vehicle rolled into the eastbound ditch.
Police say nobody was injured in the incident, but the highway was initially closed for about 90 minutes during an investigation and while workers transferred fuel to a standby unit.
They say only a small amount of fuel leaked from the truck, and there's no indication speed or alcohol were factors in the accident.
Police say they expected to close the highway again so workers could operate a crane and remove the remaining fuel from the truck.