The driver of a tanker truck that spilled as much as 30,000 litres of fuel into a Vancouver Island river is under investigation for drunk driving and the assault of a police officer.

The Columbia Fuels tanker truck rolled over early Saturday evening on Highway 1 at Goldstream Provincial Park, damaging the tank and spilling fuel into the Goldstream River.

The 33-year-old driver of the truck was arrested at the scene of the crash and police say he is under investigation for impaired driving and assaulting an RCMP officer during his arrest. The officer was not seriously injured in the alleged attack.

Columbia Fuels has suspended the driver, a Nanaimo resident who escaped the crash without major injuries. The company insists it will work with local First Nations and environmental specialists to mitigate the damage.

The environment ministry says the spilled fuel could impact fish in the area for years.