Two properties in the Waimate district are under movement controls by the Ministry for Primary Industries (MPI), over concerns of the cattle disease, mycoplasma bovis.
The restrictions, which limit the movement of animals off the farms, comes after suspicious test results for the bacterial cattle disease.
The properties were identified through MPI's surveillance program which has tested more than 40,000 samples of milk, blood and swabs.
"This is exactly why we are doing this testing work - to know where the disease is in order to contain and remove it," says MPI director of response Geoff Gwyn.
"We do not believe the new suspect properties represent a game changer.
"These farms are in the same geographical area to all known infected properties and neighbour Van Leeuwen Dairy Group farms."
Mycoplasma bovis is spread through close and prolonged contact between animals and through the direct movement of stock.
"We do not believe there is a significant risk of disease spread across fences," Mr Gwyn said.