A handwritten list of contact details for 20 people from the lower North Island is the subject of a police investigation after it was recovered by police.

The list was discovered as police responded to an incident involving people unlawfully on a property in Wellington last Monday.

A police spokesperson says officers have since determined the list of names relates to firearms licence holders in several locations across two different police districts.

"We have also determined the list was not sourced from police records which have been reviewed, and some of the detail is outdated and does not match current firearms records.

"Te Tari Pūreke – the Firearms Safety Authority — was alerted on Friday and over the weekend staff identified a commonality among those on the list with regard to firearms licence type.

"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. 

"The focus of our ongoing investigation is to understand how this list was compiled.

"Te Tari Pūreke is now working with the affected licence holders to identify possible sources of this 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."