Police believe the people who have slaughtered sheep at night inland from Gisborne in recent months, and stolen the meat to sell, are experienced farm workers who live in that area.
Farmers met police early last month to work out strategies to try to catch the people responsible.
Integrated Foods lost 145 sheep from its Whatatutu farms over summer, another farm lost 56 ewe hoggets over a few nights in March and another farm lost 23 ewes in February.
All the stock were slaughtered in their paddocks or in yards, and the heads and guts left behind.
"We believe those responsible are experienced farm workers who know how to slaughter stock properly," said Te Karaka Constable Paul Cleaver.