State Highway 1 is now clear after a 4am crash in the Dome Valley where hundreds of litres of diesel spilled from a truck's fuel tank onto the road.
Two people were injured when a car and a truck collided on SH1 near the intersection of Goatley Rd, north of Auckland.
One person had moderate injuries and the other had minor injuries.
At one point the road was down to a single lane while emergency services cleared the wreckage and diesel, which was leaking from the truck's broken fuel tank.
By about 6.45am the road was clear.
About 200 litres of diesel spilled on the road, said fire service spokesman Jaron Phillips.
The Auckland Council had also been called to attend over concerns the diesel might spill into waterways, police said.