Almost 200,000 chickens are dead after a Helensville poultry farm was hit by a power cut.
Early on Friday morning, one of the farm workers found the bodies of around180,000 birds that had suffocated.
The equipment which pumped air into the sheds failed when the generator didn't kick in after the power cut, reports Fairfax.
The Ministry for Primary Industries (MPI) confirmed to Newshub an "incident" at the farm resulted in the deaths of a large number of chickens due to "a power failure and a subsequent generator issue".
Director of Compliance Gary Orr says any such incident is of extreme concern, and MPI is investigating the deaths.
The farm reportedly supplies Tegel Foods which confirmed a power loss had occurred.
"A power interruption on the grid and the subsequent failure in the backup systems has resulted in the loss of birds from a farm," a spokesperson for the company told Fairfax.