A 40-tonne truck has crashed in Pokeno, south of Pukekohe.
Pokeno Road is closed and diversions are in place while a crane is brought in to lift the truck.
Police say power is cut to the Tuakau area as power lines have come down.
The driver was not injured.
The incident occurred just before 2am on Monday and the road is expected to be closed until about 8.30am.