Police say a serious crash has closed State Highway 2 near Bombay, south of Auckland.
The crash happened just east of the intersection with State Highway 1.
Police said traffic diversions were in place along Koheroa Rd and Island Block Rd.
Heavy motor vehicle drivers were advised to use Island Block Rd or "other suitable routes".
Police urged motorists returning to Auckland from the Coromandel or Bay of Plenty to either delay their journey or use alternative routes away from the crash.
St John was alerted to the accident at 2.36pm and sent a rescue helicopter and four ambulances to the scene.
The incident happened on State Highway 2 near Avon Rd and the State Highway 2 intersection.
All patients were taken to Middlemore Hospital.
St John said four patients were in a serious condition, three were moderate and one had minor injuries.
A police spokesman said they were called to the scene at about 2.40pm.
Two vehicles were involved and 11 people were assessed by St John for injuries, he said.
A spokeswoman for the Fire Service said one person was trapped during the incident and had been flown to hospital in a serious condition by the Auckland Westpac Rescue Helicopter.
Five others injured were believed to be children, she said