Documents including firearms licensing information and personal details have been stolen from the former Auckland Central Police Station.
The former Auckland Central Police Station. Photo: RNZ / Kim Baker Wilson
Four people had been charged to date, Auckland City District Commander Superintendent Karyn Malthus said.
Police are now contacting people whose documents have been obtained as a result of the burglary.
There was nothing to indicate any involvement of organised criminal groups in this burglary at this stage, Malthus said.
The matter was being taken extremely seriously and a "significant" investigation was under way.
"Our investigation is continuing to work to understand the full breadth of documentation that was stolen."
Four people had been charged with burglary and receiving stolen property offences.
The police headquarters moved from the old Auckland Central Police Station, on the corner of Vincent and Cook Streets, to a new building on College Hill in 2019.
Meanwhile, a gun group has reacted with outrage over the theft.
The Sporting Shooters Association is calling for the new firearms register to be abandoned, saying the police have clearly been negligent in protecting important personal data.
President Chaz Forsyth said gun owners' main objection to a firearms register was that data might be stolen and used as a shopping list to source firearms.
Forsyth said the incident reinforced that argument.