Emergency services are responding to a serious crash on State Highway 2, Horokiwi, between Wellington and Petone.
At about 4.15am a single vehicle crashed into a power pole and caught fire.
One person was critically injured, another person suffered serious injuries, and a third person received minor injuries, a police spokesperson said.
The power pole and lines are down and the northbound lane of SH2 is closed.
Diversions are in place and the southbound lane remains open.
Motorists are asked to avoid the area or delay travel, if possible.
The serious crash unit will examine the scene and closures may be in place for some hours.
Meanwhile, two people died after two crashes on SH1 in Northland last night.
The first was a two-vehicle crash south of Kaitaia, near the intersection with Clough Road, just after 5pm.
Four people were airlifted to hospital in serious conditions.
Another person died after a head-on crash between two cars towing trailers north of Okaihau, in Northland, shortly after 7pm.
Two occupants of the other vehicle suffered moderate injuries.