Households regularly putting general rubbish into their recycling bins will have them taken away, Auckland Council warns.
New recycling rules came into play in February and the council said it had been monitoring bins since then.
Parul Sood, the council's general manager waste solutions, said it was not unusual to find loads contaminated with rubbish.
"We are actually monitoring bins at the moment to see whether people are misusing them and the main concern is gross contamination."
Several items such as aerosol cans, lids and aluminium trays that could previously be recycled were no longer allowed.
Council warning for those misusing recycling bins
But the recycling loads being processed at Auckland Council's recovery facility in Onehunga showed the region's bins were contaminated with a lot more than that.
Dirty nappies, old shoes and even a wire dish rack were just some of the items that were being removed from recycling at the facility.
Sood said repeat offenders would be educated, then given three warnings.
The final step would be to take the bin away and replace it with a clear bag for recycling.
"The last load, a truck that actually caught fire had a lot of electronics in it. And you think, 'well, what's that to do with recycling?' So we just need to remember it's for packaging type only, that comes out of your kitchen, laundry or your bathroom.
"(The recycling bin) is not meant for anything else."
At the recovery facility, workers wearing gloves and masks manually sorted the recycling before it went into a large machine.
Workers sort the recycling at the Onehunga recovery facility. Photo: Mahvash Ikram/RNZ
"When the material comes in, it gets onto a massive conveyor belt and there are people standing there that pull out gross contamination and it's quite disgusting for them to pull it out, but it does get pulled out and it goes into the rubbish pile," Sood said.
Most milk bottles passing through on the conveyor belt still had their lids attached.
Under the council's new recycling rules, all items less than 50 mm and all lids must go in the rubbish bin.
Sood said there were multiple reasons for that decision.
"One is because what people were doing was leaving liquid in the bottle and then putting it the lid back on."
She said lids sometimes also fell into the machinery.
Sood said it was best not to flatten milk bottles completely "like a piece of paper" because that caused problems in the sorting equipment.
Huge conveyer belts carry the recycling through the facility. Photo: Mahvash Ikram/RNZ
It was also fine to put the bottles into the bin without squashing them,
"When it goes in the truck, it compacts it a little bit in any case. But if you are making it absolutely flat, then there's a problem to actually sort it."
Machines at the facility were equipped with technology to detect and remove items that were not allowed.
But Sood said people must be careful about what they put in their recycling bins because contamination comes at a cost.
"The machine is not there to pick your rubbish out," she said.
"If (rubbish) does make into the pile you are actually getting the pile's value down ... and that will cost you and me more."
She said while people were still getting used to new recycling guidelines, plenty of items that should never never be put into recycling bins still showed up.
"If it's a soft plastic, which means you can squish it, you can make it into a ball, that also does not go in your recycling bin because it can get entangled in the machinery."
Sood said people often put their recyclables in a bag, which was also incorrect.
"It has to be loose."