Fuel is leaking onto State Highway 2 in the Bay of Plenty after a large truck rolled east of Pukehina.
The truck's driver is unharmed, but the vehicle has blocked both lanes of the road.
Emergency services are at the scene, and the road is expected to remain blocked for at least an hour while the truck is moved and the fuel cleaned away, police say.
Diversions are in place.
"Traffic travelling east should take the alternative route by turning off SH2 at Pukehina Station Rd before travelling to Old Coach Rd and then returning back on to the State Highway.
"West bound traffic should use the same route, leaving SH2 at Old Coach Rd before turning onto Pukehina Station Rd and re-joining SH2 west of the crash site."