A diesel tanker has rolled down a bank in Whakamaru, 3km south of Kinleith.
A police media spokeswoman said the crash was on State Highway 32, between Kauri and Waikato roads.
She said the driver was out of the tanker and was being checked over by ambulance staff.
The Commercial Vehicle Investigation Unit was attending and a hazardous materials unit was on its way.
She said the road was not blocked but motorists should be cautious driving in the area and expect delays.