State Highway 1 has been closed in both directions at Dome Valley, north of Warkworth, after a two-car crash.
One person is in a critical condition, two are seriously injured and a fourth person has sustained moderate injuries.
Emergency services are at the scene and the Serious Crash Unit has been notified.
Diversions are in place at Wayby Valley Road at State HIghway 1, and at Kaipara Flats Road South.
Motorists are asked to be patient and avoid the area where possible.
ENDS
Issued by Police Media Centre