Two people are trapped in vehicles after a head on collision State Highway 1, north of Whangarei.
One is in a critical condition and the other is in a serious condition, police reported.
Emergency services were called to the scene in Whakapara, between Russell Rd and Old North Rd, at 12.55.
Three fire engines are at the scene as are police and ambulance.
A fire service spokesman said police had closed the road, and the NZTA has tweeted that drivers should follow the directions of emergency services and expect delays.
Diversions are in place and the serious crash unit will investigate.
Click here for NZTA's detour route.