UPDATE 3.50pm:
Police have confirmed the driver of one of the vehicles involved in a head-on collision has died at the scene.
Sergeant Simon Craig said four other people from the two vehicles were taken to Whangarei Hospital with various injuries.
The road remains partially closed as police interview people at the scene and continue their examination.
The death takes Northland's road toll to 16.
UPDATE 3.17pm:
Emergency services have managed to clear part of the scene and have now opened the southbound lane for traffic. However, northbound traffic will continue to be diverted.
2.15pm: A crash involving two vehicles has closed State Highway 1 near Oakleigh, south of Whangarei.
The head-on crash between two cars happened just after 2.00pm near the intersection with Totara Rd and one person is reported to be trapped.
The driver of one car was in a critical condition and four others were reported to have sustained moderate to serious injuries.
The state highway has been closed and diversions are in place using Springfield Rd for traffic heading south and northbound traffic to be diverted through Salmon Rd.
It is estimated the diversions will be in place for at least two hours and motorists can expect delays.
Police, fire and St John ambulance were all at the scene.
The woman was recovered from the water and received CPR.