Gun collectors are being warned to be on the lookout after an arsenal was stolen in Northland earlier in the month.
Fifteen firearms were stolen from a Dargaville property on May 17 - some of them valued at $5000 each - with police saying they were worried they would be in the hands of criminals.
Investigators now say other gun collectors and enthusiasts in the area have been receiving suspicious phone calls which may be aimed at finding out if they're home.
They have included calls where the caller hangs up without saying anything.
"Establishing whether this has any link or not to the recent firearms theft in Dargaville is a priority for us, but as we continue our enquiry we are warning anyone with firearms to ensure they are stored securely," Detective Andrew Bailey said.
He said owners should try to hide the keys to their gun safe to make any burglar's job as hard as possible.
Police are also warning ammunition retailers about anyone asking for ammunition for AK47 and AK74 guns, which were among the stolen weapons.
Any gun owners who receive suspicious calls have been asked to report them to police.
The weapons and their serial numbers are: