Six people were hospitalised in a crash between two cars and a stock truck on State Highway 29 near Maungatapu.
The crash happened about 7pm yesterday.
Sergeant Wayne Hunter said a car and a stock truck had collided on the highway between the Maungatapu Bridge and the Maungatapu roundabout. A second car was then in a collision with the first car.
The stock truck was empty because it had recently been unloaded.
Mr Hunter said two of the five occupants of the first car and the lone occupant of the second car were trapped in their vehicles.
In all, six people were hospitalised. One person from each car had serious injuries, the other four had moderate injuries.
Both of the cars were badly damaged in the crash and the truck had two burst tyres.
Debris was strewn across the road, with part of one car's door lying about 20m from the vehicle.
Three ambulances, two fire trucks and multiple police cars were at the scene.
The section of State Highway 29 between Maungatapu Bridge and the Maungatapu roundabout was closed for more than two hours while the crash was cleared.
Traffic was diverted through Maungatapu Rd.
A woman in a nearby house, who spoke on the condition she was not named, said she heard the crash.
She came to see what had happened and saw other residents rushing to the crash with jackets and first aid kits.
"I think all the residents around here know when you hear a big bang to come out with all your gear."
In October 18-year-old Calum Gilmour died in a car crash on the other side of the Maungatapu bridge.