Kaipara District Council general manager customer experience Darlene Lang said the council's focus was ensuring the welfare of the animals and all those involved.
"As the investigation is ongoing, no further comment on actions and outcomes can be made at this time. We're asking for patience as we address the situation. "
SPCA Inspectorate general manager Tracy Phillips could not provide comment on the specific case because it would breach the owners' privacy, but said when the SPCA did investigations, they collected all of the facts and made decisions based on "the right outcome for the animals".
"If we go into a property and simple take animals, people will simply restock," she said.
Phillips said the SPCA worked with owners on a plan to achieve "the right outcome", but could not say what was happening in this situation.
"If we want to retain our approved organisation status, we have to do things in accordance with the law. We have to be reasonable about it.
"If we needed to and there was an urgency around it, then animals would be uplifted from the property."
But Huha co-founder Carolyn Press-McKenzie said the puppy mill near Dargaville was just one of "quite a few" the organisation has been looking into.
She said while owners of puppy mills were able to tick the "food, water and shelter" boxes, many dogs and puppies were unsocialised and suffering from significant behavioural issues, meaning they were "not coping in their new homes and not appropriate for new homes".
The law required the dogs' behavioural needs to be met, but nobody was enforcing that part of the law, she said.
"It's not an isolated situation, and that's what's incredibly disturbing."
Press-McKenzie said many people would think the mills were being run by "some misguided old lady", but there was more to it beneath the surface.
"It's big business, it's big money, and it's very well organised."
New pet owners usually wanted to do the right thing when buying a puppy, but once they see a photo "they're a goner".
"They justify taking that animal even if they have concerns."
She encouraged people wanting a purebreed dog to go through reliable organisations, such as Dogs New Zealand, formerly known as the New Zealand Kennel Club.