They included a visiting couple who were killed in the accident.
The two were married and believed to be in their 50s.
The 33-year-old female driver, who is a North Island resident, was uninjured, while the front passenger was flown to Invercargill hospital with a lung injury.
Police have said neither alcohol nor the weather were factors in the crash.
They would not release names until families had been contacted.
Two helicopters, police and fire service personnel attended the scene on Wednesday about 7pm, and it was understood one helicopter used a winch to recover the crashed Subaru Forester.
The crash occurred on the Milford side of the tunnel, about 1km from the entrance, and the vehicle fell about 5m down a bank beside the road.
Two fire crews, St John, police, Department of Conservation workers and two doctors at the scene worked to rescue the injured person and recover the bodies of the two dead before darkness fell.