A large number of chickens have died after a power failure at what's believed to be a Tegel farm in the North Island.
The Ministry for Primary Industries said about 190,000 chickens died in the early hours of Saturday at a chicken farm in Helensville.
The ministry's director of compliance, Gary Orr, said the deaths were "due to a power failure and a subsequent generator issue".
"Any such incident is extremely concerning to us and we are now investigating," he said.
Marianne Macdonald, animal rights group SAFE's campaign manager, said the deaths were unacceptable.
"It's the chicken industry's responsibility to ensure disasters like this don't happen. They need to have back-up systems," she said.
"It's quite clear that they're treating those poor birds as units of production rather than sentient animals that they are, who suffer."
Tegel has been approached for comment.