Two people were critically injured when the car they were in rolled off the road on State Highway 6 near Blenheim today.
Emergency services were called to the crash at Okaramio about 12.36pm.
Police said the incident involved two adults and two "younger people" in a single vehicle, Stuff reports.
In a statement, police said two people had sustained critical injuries.
The police serious crash unit had been notified and an investigation is under way.