Police said a scene examination has been carried out at a house in Māngere Bridge.
“Police are continuing to establish the circumstances leading to the woman’s death and can confirm the victim and alleged offender were known to each other.”
Formal identification of the woman is still to be completed, police said.
The development comes after a man turned up to the police station last Friday afternoon and approached the counter.
The woman was found dead in a vehicle shortly afterwards.
A Māngere Bridge property was later cordoned off with emergency tape and a white forensic tent put up in the front yard.