The SPCA has rescued about 180 cats from an Auckland home living in filthy conditions.
Chief executive Andrea Midgen said some of the cats were being kept in very small cages, some did not have access to food or water and the owner did not know how many cats were on the property.
"There was a lot of filth, a lot of faeces. The ammonia count was at alarm levels," she said.
Ms Midgen said the SPCA had visited the residential property a few times as a result of complaints, but would not say where it was or give any details about who was keeping the cats.
About 15 SPCA staff, including most of the dog staff, have been assessing the cats since they were removed from the property yesterday(Thursday).
The SPCA has advised the public not to bring cats to its Mangere shelter until further notice.
There were between 140 and 150 cats at the shelter before the rescue operation, the largest on record.
Ms Midgen described the case as "good intentions gone haywire".
Despite the "unbelievable, abominable" living conditions, she said the cats were in a better way than first thought.
Some needed medical attention, but there were no life-threatening conditions.
The SPCA is carrying out an investigation into the case, which could lead to a prosecution.
The investigation will determine the future of the cats.
The shelter is unable to accept any cats for at least a week, perhaps longer.
"The decision to halt cat admissions is not taken lightly. We simply have no space left," Ms Midgen said.
She said the SPCA would happily provide people with help and advice on finding a new home for cats.