Police and Fire and Emergency services were called to a single vehicle accident on Kohi Rd, between Karahaki Rd and Hughes Rd, near Waverley around 10.20pm on Saturday.
A police spokeswoman said one occupant of the vehicle had left the scene by the time they arrived, while one was still there.
Police eventually located the person who had left, she said.
An ambulance was called to treat one patient with moderate injuries, a St John spokeswoman said.
The person did not need to be taken to hospital.
