Drones are helping determine the impact of fuel spilled into the Fraser River near the western entrance of Mount Robson Provincial Park when a tanker truck crashed on Wednesday.

As many as 20,000 litres of diesel was spilled when the truck towing two tanker trailers rolled onto its side.

The incident took place on a curvy, slushy stretch of Highway 16 approximately two kilometres east of the park's visitor center.

No one was injured and the truck has been righted, but officials don't yet know how much of the spilled fuel entered the nearby Fraser River.

Witnesses have described an oily sheen and the smell of diesel down river from the crash site.

Mount Robson tanker truck crash

The tanker truck rolled over along a twisting section of Highway 16 near the entrance to Mount Robson Provincial Park early Wednesday morning. (CBC)

B.C.'s Environmental Emergency Response crew is on-site assessing damage and using drones to survey the area. They are also drawing up a plan for long-term monitoring and sampling of the site.

The truck belongs to Federated Co-operatives Limited, which dispatched its clean-up crews, including vacuum trucks and excavators, to the crash location.

An official with B.C.'s Ministry of Transportation said there are signs along the highway warning of the curves in the road, and a truck was sanding the route just prior to the accident.

Google Map: Mount Robson Provincial Park Visitors Centre