The Waikato Regional Council says crews are salvaging a tanker that rolled off a road on a farm near Pukekohe and started leaking fuel into a nearby waterway.
Fire crews called to the scene in Buckland at about 7am rescued the driver, who was trapped uninjured in the cab.
The council said though the tanker is carrying 13,000 litres of diesel and 8,000 litres of petrol, the leak is from the engine, not the tanker itself.
It said trucks were at the scene sucking the fuel out of the tanker so it could be righted.
The council said the small amount of fuel that leaked into a tributary of the Whakapipi stream was not a significant environmental threat.