Wellington's Transmission Gully is closed after a crash involving a fuel tanker leaked around a thousand litres of petrol, raising fears of an "explosion".
Waka Kotahi NZ Transport Agency (NZTA) said the crash, which was reported at 5:40am, happened about 3km south of the Paekākāriki offramp.
State Highway 1 between Pāutahanui and Paekākāriki is closed in both directions.
Fire and Emergency New Zealand (FENZ) said they have dispatched several crews to the site of a "significant fuel spill" on Transmission Gully following a crash between a fuel tanker and another vehicle.
"Seven fire trucks, including a Command Unit/Hazardous Materials Unit, remain in place, with fresh crews relieving those who first attended the scene," FENZ said.
In an update at 11am, FENZ said decanting from the fuel truck involved in the car crash to a second fuel tanker is continuing.
FENZ said approximately 1000 litres of 95 octane fuel was spilled, but the leak has been contained.
FENZ expect the decanting of the remaining petrol to take at least a few more hours.
Fire and Emergency Group Manager Gareth Hughes said safety remains the priority for crews working to clean up the spill on Transmission Gully.
"The road will remain closed during this time as we continue to monitor the area, including using gas detectors to ensure the people from the fuel company are safe as they complete the decanting."
In an earlier update, FENZ said fire crews have set up a dam and isolated the fuel leaking from a tanker involved in the crash.
Hughes said volunteer and career firefighters are working hard to prevent it from reaching an environmentally sensitive area.
"A second fuel tanker is being brought to the site to decant the remaining fuel. Until that is complete, there is still a risk of an explosion so the road is remaining closed," Hughes said.
FENZ said an environmental protection officer is at the scene.
Police said the road is expected to be closed for "some time" and warned motorists to expect delays and use alternate routes.
Police added there were no reports of injuries but fuel is leaking from the tanker.
NZTA urges northbound drivers to use SH58 or SH59 before getting back on to SH1. For southbound drivers, motorists are asked to use SH59 as a detour.
