Police are blaming the online gun database privacy breach on "human error".
The database allowed people to notify police they have a prohibited firearm or related item. But earlier on Monday, it was revealed there had been a privacy breach which made gun owners' details available online - including names, addresses, dates of birth, and bank account numbers.
Police say the breach occurred when an update to the database - which was not authorised by police - gave a group of gun dealers more access to the database than they were supposed to have.
"Upon being notified all efforts were made to immediately shut down access to the platform," says Deputy Commissioner Mike Clement.
"We believe this was an isolated incident and made possible due to human error."
Clement says the buyback programme will continue, however police will go back to a manual process until they can be reassured that the online platform is secure.
The vendor in charge of the web page was German-based software company SAP, which has apologised "unreservedly" to Police and New Zealand.
"The security of our customers and their data is of absolute priority to us. A full internal investigation is already underway within SAP," a spokesperson says.
"We continue to work with and offer our full resources to New Zealand Police to ensure the system is fully secure and up and running again as soon as possible."
The Council of Licenced Firearms Owners told Newshub gun owners who had used the site may need to increase their security.
"They were able to screenshot and download information. This means that gang members or other criminal elements could have accessed this information before our supporters found the breach," a spokesperson says.
"Keep an eye on your bank account - possibly notify your bank to stop unusual transactions. You may consider whether you should take extra personal and home security precautions.
"This is exactly what we feared of an incompetent agency in charge of an online register."
But Clement said that based upon current information firearm holders didn't need to take any extra measures.
He said people still need to follow the law and hand their guns in.