Holidaymakers heading south from Northland are stuck in near-standstill traffic after a crash at Puhoi.
Police said one car went over a bank on State Highway 1 near Schollum Access Rd, leaving a person in a critical condition.
Traffic is being controlled by Stop/Go operators and is extremely heavy heading south. The New Zealand Transport Agency says motorists should consider using State Highway 16 instead.
Northbound traffic is also backed up to the Johnstone's Hill Tunnel.
Journalist Jerram Watts reached Warkworth at about 2:40pm and estimated he had travelled about 2 kilometres in one hour.