Rumours of a South Island black panther have resurfaced after a sighting on Friday night.

Photo: 123RF

Picton couple Juliearna Kavanagh and Warren Lewis claim they've seen the mystery beast on the prowl near Ward, while driving on State Highway 1.

There have been about 10 reported sightings since the 1990s and MPI aren't ruling out a case of mistaken identity, but Ms Kavanagh, an entrepreneur and hotelier, said she knows what she saw.

"It was a great big thing with a head that was a cat and then a long body... sleek, black and with a very long black tail. It was about the height of my knees, maybe a bit taller than my knees," she said.

"It was in full flight, running about 10 meters from us in the headlights."

She had just slowed for a corner, and said she did a double take. The two immediately turned to one another in awe, wondering if they had both seen the same creature.

Ms Kavanagh grew up on a farm and Mr Lewis is a keen hunter - but he said neither have laid eyes on anything like it in their lives.

"It definitely wasn't a dog. And it wasn't a pig. It wasn't any of those. It was a big cat... and it was amazing," he said.

Ms Kavanagh was not aware of the South Island big cat rumours, but said a call to her father sent her into "research mode." He told her "this thing has been seen before".

The mystery of a South Island big cat dates right back 1992, when it was first spotted lurking near the Ashburton River Mouth. There have been sightings from Mid Canterbury to Bluff to Kaikoura; on farms, in forests and once in a photograph, strolling across a frozen lake.

It has been variously described as a panther or puma - but all descriptions point to a dark creature the size of a dog with a large head and a long tail.

In a statement, MPI confirmed that they had received one sighting last week of a large cat.

"We have previously received calls over many years about similar sightings in the north and south islands. MPI has investigated photographs, footprints and hair, scat and faeces samples, and in each of those previous cases, we have concluded the sighting to be that of either a dog or a large feral cat."

DOC Operations Twizel Manager, Sally Jones, said their biodiversity rangers had also caught a few big cats, but no mountain lions to date.

"The biggest was not much smaller than a Labrador," she said.

"Feral cats have the same appearance as some common, short-haired house cats such as tabby, tortoiseshell and black. They can grow to a much larger size than house cats, though they don't live as long. Male feral cats captured in the South Island high country averaged a weight of 3.75 kg and the heaviest male weighed 7 kg."

Ms Kavanagh said if one of her staff had come to work telling her about seeing the big cat, she would have been dubious. But having seen it with her own eyes, she is sure.

She hoped one day the sightings will add up to solid proof.

"Eventually somebody will find one or somebody will shoot one or somebody will cage one or something will happen. MPI, I believe, already know because there's been poo, and markings and droppings," she said.

"I'm 110 percent sure, absolutely, that there are big cats wandering around the South Island and New Zealand."