Over the weekend staff found a number of people on the list appeared to have similar firearms licence types.
Te Tari Pūreke has begun contacting people on the list to advise them of the situation.
The authority is also contacting relevant shooting clubs associated with people on the list, to understand if their club records could have been compromised.
Police said the focus of their ongoing investigation is to understand how the list was compiled, including working with affected licence holders to identify possible sources of the information.
“There are several lines of inquiry being pursued. Te Tari Pūreke is urging all shooting clubs and ranges to check the security settings they have around information collected about club members and/or visitors, including historic records from past activities”
Georgina Campbell is a Wellington-based reporter who has a particular interest in local government, transport, and seismic issues. She joined the Herald in 2019 after working as a broadcast journalist.