The Independent Police Conduct Authority (IPCA) will investigate the death of a teenager flung from a car as he fled from police in Oropi, near Tauranga.
The car 18-year-old Levi Green was in fled when police signalled for it to pull over, and accelerated over a bank.
Police say the crash happened so fast that officers had not officially declared a pursuit.
But the incident was automatically referred to the IPCA.
Police had been called to a party in Oropi, south of Tauranga, at 11pm yesterday after reports that someone had been struck by a car.
They said when they neared the house they tried to pull Mr Green's car over for having no tail lights, but he fled.
The car went over a bank and Mr Green was thrown out. The Tauranga teenager died on the way to hospital.
A police spokesperson said officers were still trying to piece together what happened, but an initial scene examination had shown not wearing a seatbelt was a factor in Mr Green's death.
She said police were interviewing about 150 people who were at the party.
Witnesses told officers the car had earlier been seen at a party and was later seen driving erratically on Mountain Rd.
Police said Mr Green's car was not the one that had earlier struck a partygoer after about a dozen gatecrashers were involved in an altercation.
The person struck by the car was not seriously injured.
