The SPCA has confirmed several dogs were found dead in a vehicle on an Interislander ferry on Monday night.
An investigation into what happened is underway, with authorities apparently reluctant to discuss the matter.
The dogs were found in a ute on the vehicle deck of the ferry. The SPCA confirmed several dogs were found in an aluminium dog box on the ute tray.
They wouldn't confirm how many 'several' were, but it's believed to be at least five.
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"Three others had to be humanely euthanised due to the extent of their condition," the SPCA said in a statement.
"A thorough investigation is underway by our vets and experienced SPCA inspectors."
They wouldn't comment further.
The Interislander operates three ferries between Picton and Wellington, with around 4000 crossings of the Cook Strait each year.
Its website details what to do if bringing pets on a crossing.
"During peak season, we recommend you book a kennel if you are bringing a pet, as we cannot guarantee shaded parking will be available."
"Your pet can remain in your vehicle for the journey for no extra charge... you must inform check-in staff that you have a pet in your vehicle. It must left ventilated with water for the animal."
Kennels can be added to a booking for $15, which it says are in a cool, well-ventilated area.
Kiwirail, which operates the Interislander, says it makes it clear that keeping pets fed and watered is the owner's responsibility.
Kiwirail told Newshub it's a system that's been in use for many years ,and that they are loathe to stop this practice for the majority who take responsibility for their pets and follow the recommended guidelines.
Police confirmed they did attend the incident, but say the SPCA is responsible for investigating and prosecuting animal neglect and cruelty, and it would be inappropriate for them to comment further.
Kiwirail described the deaths as tragic and distressing for everyone involved.