Detective Warren Duncan, who is also investigating the recent shooting of 195 sheep on Peter and Janine Stackhouse's nearby farm, believed at least another 15 sheep were killed on Sunday night.
They were found yesterday morning by a ''very upset'' property owner, he said.
Mr Stackhouse yesterday was reluctant to comment on the latest incident for fear of drawing attention to his property, but said the area would be ''absolutely devastated'' and ''really, really nervous'' after the latest incident.
''We are really struggling ...,'' he said.
Asked if there was anything residents could do, such as forming some sort of patrol or neighbourhood watch, Mr Stackhouse said that was possible, but quite difficult to set up in a hurry.
It was a matter of people in the area looking out for each other, locking up gates, being very observant and reporting anything that looked even slightly out of the ordinary, he said.
Det Duncan said police yesterday examined the scene of the latest incident.
He understood the sheep were not insured.
Once again, they were on land away from the road.
It was too soon to comment on how the sheep died or whether their deaths were linked to the incident on the Stackhouse farm.
''Both of these events are very unusual but we appreciate they will be creating a high level of concern among local farmers and the community in the area,'' Det Duncan said.
''If locals have concerns about their property security, then please contact Oamaru police for advice and support.
''Our general advice is, as much as possible, to be vigilant about securing your property and stock.
''Keep an eye out for any suspicious vehicles or people in your area. Talk to your neighbours and look out for each other.''
Regarding the latest incident, police would like to hear from anyone who saw suspicious vehicles or people in the area of Crown Hill, Conlans and Peaks Rds on Sunday night or early yesterday.
Federated Farmers is asking political parties to develop policies to tackle rustling, which it estimates costs farmers $120 million a year.
Its rural security spokeswoman, Katie Milne, used several recent incidents, including the Ngapara stock shootings, to question whether penalties were strong enough to be a deterrent.
''Based on our experience to date, they are not,'' she said.
''We need political parties to take this seriously because in many instances weapons are being used. We would welcome parties to engage with us because the level of violence is appalling.''
