He said both cars were badly damaged.
Hato Hone St John attended with two ambulances and treated two patients.
Both patients were taken to hospital by ambulance in a serious condition.
Fire and Emergency NZ and police also attended.
“Police received a report of a single-vehicle crash where a car has gone down a bank on Lighthouse Rd,” a police spokeswoman said.
Emergency services could be seen going down a private driveway to reach the crash site.
Motorists were being advised to take care around the area.
Another resident, who did not want to be named, said he heard a woman calling “help me, help me” after the crash.