Tens of thousands of chickens died of suffocation at a farm. (File picture)

Almost 200,000 chickens were found dead after suffocating when a power failure hit a poultry farm.

​Stuff was told a power cut impacted the poultry farm, on the outskirts of Auckland, and equipment that was pumping air into the sheds stopped working as the backup generator failed.

Stuff understands an alarm failed, a worker early on Friday morning found about 180,000 chickens dead and the animals were later disposed of at a worm farm.

Safe / Stuff Broilers packed into a shed at five weeks old are a feature of some New Zealand poultry farms. (Video, produced by animal rights charity SAFE, was first published October 18)

The Ministry for Primary Industries confirmed it was investigating the "deaths of a large number of chickens".

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"After being alerted to this issue today, and having spoken to the company involved, we have had it confirmed that there was an incident in the early hours of Friday morning at a chicken farm that resulted in the deaths of a large number of chickens due to a power failure and a subsequent generator issue," an MPI spokeswoman said.

As a result of the suspected equipment failure, it was thought that about 180,000 chickens died at the farm, which supplies poultry company Tegel Foods.

Tegel confirmed that "a power interruption on the grid and the subsequent failure in the backup systems has resulted in the loss of birds from a farm".

In a statement on Monday, the company added: "Tegel is working closely with all its contracted growers to ensure contingency systems are in place and working correctly."

Hans Kriek of animal welfare group SAFE said it was an appalling incident.

"The onus is on the humans to make sure nothing goes wrong."