The police are warning farmers in Akaroa, in Banks Peninsula, that thieves who have slaughtered sheep and stolen wool from three local farms could strike again in the holiday period.
They say a farmer in Birdlings Flat had two lambs and 10 ewes, several of them pregnant, butchered in the paddock over the past nine months.
About 30 bales of wool were also stolen from two different farms this month - one off Stony Bay Road and one on Birdlings Flat.
The police believe more than one person is involved in the thefts because the bales weigh about 170kg.
Farmers were urged to padlock access gates and woolsheds.
Anyone who sees suspicious behaviour in the area is being asked to contact the local police station.