Two people have been freed from their cars after an accident involving a truck and trailer and two cars on SH1, Wellsford.
A fire communication spokeswoman said they had three fire trucks at the scene, and they had extracted the two patients.
Police said they were notified of the incident at 2.27pm; they were currently in attendance at the scene.
One person has been airlifted to hospital with critical injuries. A second person is in a serious condition.
Part of SH1 remains closed.
Waimanu Road in Wellsford is closed in both directions.
The Serious Crash Unit is investigating and Waimanu Road is expected to remain closed for at least two hours.
Diversions are in place at State Highway 1 and Mangawhai Road, and at State Highway One in Kaiwaka.
Motorists are asked to be patient and avoid the area if possible.
Both police and NZTA are advising motorists to take extra care as heavy rain around the greater Auckland area is making the roads slippery.