MPI confirms 200-thousand birds will now be killed, at an Otago egg farm managed by Mainland Poultry - infected with bird flu

A fourth shed has tested positive for the disease -- and the cull will now also include 40-thousand chickens in a separate building - as a precaution.

MPI chief veterinary officer, Dr Mary van Andel told RNZ staff had already decided to kill the birds in the fourth shed, before the positive test.

She teams are about three-quarters through depopulation -- but the disposal, cleaning and disinfection work will take longer.