Five patients were treated at the scene and taken to Christchurch Hospital, two with serious injuries.
“Three ambulances, two helicopters, a rapid response unit and an operations manager were dispatched to the scene and transported two patients in a serious condition, and two in a moderate condition, to Christchurch Hospital,” said a St John spokesperson.
Fire and Emergency New Zealand (Fenz) responders also attended the scene.
“We were notified of a motor vehicle crash involving one vehicle that had rolled at 10.20am,” said a Fenz spokesperson.
Fenz sent three crews to assist police and emergency services at the time.
“On arrival, all patients were out of the vehicle and were being transported to hospital by ambulances and a helicopter,” they said.
Police said the road was blocked while emergency services were on the scene but is now clear.
Eyrewell Forest is a small rural area in the Waimakariri district, north of Christchurch.
Inquiries into what caused the crash are under way.
The incident comes after a series of crashes in the South Island involving many people.
Last month, a head-on crash between a van and a car left three people dead and two others seriously injured near Geraldine.
In July, 15 people were hospitalised after two buses rolled on the same stretch of road near Tekapo.
A month later, one person died and three others were seriously injured following a crash in Marlborough.
In April, four people died and two were injured following a horror crash between two vehicles and a motorcycle near Lake Pukaki.
This story has been updated to reflect a clarification by Hato Hone St John about the number of patients taken to hospital.
More to come.
Katie Oliver is a Christchurch-based multimedia journalist and breaking news reporter.