An ambulance on its way to a crash on State Highway just south of Whangārei has been sideswiped by another vehicle which has failed to stop.
A three-car pile up initially blocked the highway, near Puwera, just before 4pm.
Police and emergency services were quick on the scene and got traffic flowing again.
However, an ambulance called to the crash was sideswiped by a vehicle, which was last seen heading down Oaks Rd, off SH1.
No one was injured and the ambulance crew continued on their way to the scene.
Senior Constable Stephan Billings said it appeared a car travelling north in the passing lanes had to braked to avoid traffic that had slowed and started backing up because of road works.
It collided with a car in front but a second northbound car also collided with the second.
One vehicle ended up on the wrong side of the road.
A female driver was taken to Whangārei hospital with neck and back injuries.
The crash happened as heavy traffic flowed into Northland for labour weekend.
The New Zealand Transport Agency today warned motorist to take car when driving north as there are several construction sites along the way that may cause congestion and affect journey times.
Senior manager project delivery Andrew Thackwray said construction crews would not be working over the long weekend but there would be temporary speed limits and other traffic management strategies in place.
The major road works heading north included SH1 Brynderwyn Hills where retaining wall repairs were being done on the southern side. The road was reduced to one lane in each direction with a steel barrier, closure of the northbound passing lane and a 30kmh speed limit.
Another hot spot was SH1 Loop Road intersection roundabout construction. There were road cones, steel roadside barriers and 50kmh speed limit through the site area.
And finally at SH1 and Tarewa Road intersection improvements where road re-alignment had traffic using the northbound lanes and travelling 50kmh speed limit.