Police are looking for a man and a woman seen near a pawn shop in South Auckland around the time two people were killed in the shop early on Saturday afternoon.
Officers were called to the address in Great South Road in Takanini at about 1pm when a panic alarm was activated.
Detective Inspector Dave Lynch said the scene had been secured and Great South Road between Taka Street and Glenora Road would remain closed until further notice.
He said the victims had links to the business, which was open at the time.
Mr Lynch said police want to talk to a man and a woman seen leaving the property shortly before officers arrived.
"Neither of those two people stayed at the scene. We need to locate them, identify them, and find out whether or not they have any information that's relevant to the investigation."
Mr Lynch said it was in the pair's interests to contact police as soon as possible.
They are also looking for a sharp weapon that is believed to have been used in the attack.
Mr Lynch said although the victims have not yet been positively identified, police believe they know who they are.