About 200 in-lamb merino ewes, worth as much as $40,000 in total, have been stolen from Ribbonwood Station at Omarama in Otago.
Police said yesterday the theft was reported about a week ago, but occurred some time between the end of August and September 26.
The ewes were taken from a remote part of the 7289ha property.
Constable Nayland Smith, of Omarama said there were two points of access - through the farm, which would have gone past the homestead, or from Lake Ohau Rd, across Department of Conservation land.
It would have been very difficult to get a truck into the area and he suspected a 4WD vehicle may have been used, making a number of trips.
"Any information or suspicions, no matter how minor they think it is, would be welcome. If anyone noticed any strange sheep trucks or 4WDs they think don't belong, let me know," he said.
The theft was discovered when the ewes were brought in for shearing. After coming up short, a search was made by helicopter, but the missing sheep were not found.
The wool alone was worth an estimated $17,000, which, along with the ewes and unborn lambs, took the total worth of the missing sheep to about $40,000, he said.
The Omarama theft follows a report to Cromwell police in August of about 160 merino wethers, estimated to be worth about $13,000, being taken from Carrick Station.