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Last month, about 195 sheep were killed on Peter and Janine Stackhouse's farm, and about 20 sheep were found dead on Wendy and John Dodd's property, about 1.5km away, the following weekend.
Detective Warren Duncan, of Oamaru, said police were examining information received from the public, while investigating other possibilities of the cause of death by ''extending work on the sheep themselves''.
Initial investigations led police to believe that a firearm or firearms had been used.
''I've never been 100% convinced of the actual cause of death,'' Det Duncan said.
Police would consult a forensic vet for a second opinion. DNA work was also a possibility.
''I need some definitive answers,'' Det Duncan said.
''I'm exploring all avenues,'' he said.