A tractor trailer has rolled into a ditch just north of Williams Lake, B.C., dumping its load of a potentially hazardous substance.

Highway 97, 14 kilometres north of Williams Lake, has been closed since the crash which sent the truck driver to hospital with serious injuries.

A hazardous materials team is at the scene and about one dozen nearby homes have been ordered evacuated, while Wildwood Elementary school has been closed for the day.

Williams Lake RCMP Insp. Warren Brown isn't confirming what has been spilled but says it is like ammonium nitrate, a material that is used in fertilizer, but can explode if heated.

Short-term exposure to ammonium nitrate can also cause nausea, vomiting, headaches or dizziness and Brown says the decision to close the school was made because officials did not want to inconvenience students, teachers and parents as the clean-up continued through the day.

A short detour is set up around the crash and Brown notes clean-up might not begin until late morning, so there's no word when Highway 97 could reopen.