Both southbound lanes on the Hawke's Bay Expressway were covered with diesel after a spill on Tuesday night.
Emergency services were called to State Highway 2, near Frimley, about 9.15pm on Tuesday.
A Fire and Emergency New Zealand spokesman said a 1000 litre container came off a vehicle.
Police said the spill covered both southbound lanes of the Expressway. Two fire trucks were called to the scene.
"Fire fighters contained the spill and assisted with decanting with the remaining of the diesel," a FENZ spokesman sad.