State Highway 15 south of Kaikohe is expected to remain closed until Wednesday evening following a serious crash involving a car and a logging truck.
The head-on crash occurred just before 2pm on Mangakahia Road, near Tautoro.
Senior Sergeant Brian Swann of Northland police said a female driver was extricated from the car by Kaikohe volunteer firefighters and taken to Bay of Islands Hospital.
As of 5pm work was continuing to remove the truck using a heavy crane and clear the road, which was blocked in both directions.
Traffic was being diverted via Piccadilly Road, Mataraua Road and State Highway 12.
A spokesman for St John said one ambulance and one rapid response unit responded to the crash.
One patient was transported to Whangārei Hospital in a serious condition.
The police Serious Crash Unit was at the scene.