Both farmers were fattening merino-cross and Kelso-cross lambs under contract for a client when between 130 and 150 went missing from one property and about 60 from another some time in the past six weeks.
Community Constable Bruce Dow, of Oamaru, said yesterday one farmer had about 600 ewe and wether lambs on his property at a count in the last week in March.
Last Wednesday, when a buyer visited to check the lambs, another count was done and it came up short by up to 150.
He also told police a neighbouring farmer with a similar contract reported about 60 missing from his mob.
The lambs were not close to roads but remote on the farm property, away from residential buildings.
To take the lambs, a truck would have had to be driven across the farm or the lambs driven out.
Mr Dow asked people, especially farmers and stock buyers, to look out for any unusual numbers of lambs being taken to properties or being offered for sale.
The stolen lambs had a W ear mark, in the right ear of the wethers and left ear of the ewes.
Farmers and people living in rural areas were asked to report suspicious behaviour, particularly anyone loading stock who should not be there.
