A second investigation has begun into sightings of a puma-sized cat in the Hunter Valley after the ABC obtained footage of sighting on New Year's Day.

Bev Fraser said she will never forget looking down a fence line on her Hunter Valley property on January 1, and spotting what she described as a "puma-sized cat".

Key points: The NSW Department of Primary Industries is investigating a sighting of a big black cat, reported by Hunter Valley woman Bev Fraser

The NSW Department of Primary Industries is investigating a sighting of a big black cat, reported by Hunter Valley woman Bev Fraser Big cat sightings are not uncommon in regional NSW, particularly around the Blue Mountains, though most remain unverified

Big cat sightings are not uncommon in regional NSW, particularly around the Blue Mountains, though most remain unverified The department responds to them when members of the public were concerned for their safety, or for the safety of their livestock or pets

"It was just a very big, very, very, very black cat, and obviously a cat," Ms Fraser said.

"It was too large to be an overgrown domestic cat — just a 50-kilo sort of animal sitting on my fence post."

Ms Fraser, who lives on the outskirts of Maitland in New South Wales, said she had not been able to get closer than about 120 metres before the animal sensed she was there, and that she could only zoom so much to get an in-focus image.

Bev Fraser says the cat was very, very big and very, very black. ( Supplied: Bev Fraser )

She said the cat's size could be determined in relation to the sturdy fence post on which it was sitting.

"You look at it, and look at the proportion of the size of the animal to the post, and you go holy cow," she said.

"You know, it was 100 or so metres away, and that is a huge animal, and so I am still very convinced that is was a very large cat, but what variety I have no idea."

Ms Fraser said the way the cat slunk into the undergrowth was also slightly different to a domestic cat.

"I don't think it was a giant [cat] like a leopard. I think it was more sort of a puma-sized cat, but it was definitely a cat, and it very elegantly and gracefully dismounted the post when it became aware of my presence," she said.

DPI to examine the scene

The New South Wales Department of Primary Industries (DPI) told the ABC it had received the report about the big cat and launched an investigation.

Big cat sightings are not new in the Hunter and other parts of the state, particularly around the Blue Mountains.

As a result, State Government officials have a policy to deal with the sightings.

Bev Fraser's dog spent the day of the sighting barking at the fenceline, as a kangaroo watched on. ( Supplied: Bev Fraser )

The DPI said it would respond to reported sightings of large felines by referring the report to either the NSW Police, the land manager, or the Livestock Health and Pest Authority (LHPA).

The department said it responded when members of the public were concerned for their safety, or for the safety of their livestock or pets.

Ms Fraser has two dachshunds and said immediately after the sighting she was afraid to let them outside.

"I locked the dogs in the house, because I knew if they had seen it they would give chase," she said.

Ms Fraser said she was pleased the DPI was taking the sighting seriously, with an exotic animals officer planning to visit her property as soon as could be arranged.

"Basically they are going to come out and have a look at the site and I guess a closer examination of the area," she said.

"I want to know, where does it go when it is not visiting my house — and luckily it has only been there once — but where does it reside?"

Big, but most likely feral, trackers say

The Australian Big Cat Research Group is dedicated to proving that big cats exist in Australia.

It has had numerous sightings of the animals in the Hunter Valley area, and the group's founder Keven Braunton said he was keen to know more about the cat that Ms Fraser said she saw.

"Footage of it moving would help a great, and also if Bev herself could go down there and measure that fence post so we can have a reference of the size of it," he said.

Keven Braunton is the founder of the Australian Big Cats Research Group. ( Supplied: Keven Braunton )

Mr Braunton said the animal was very large, but from the footage he suspected it was an oversized feral cat.

"It is definitely like a big cat, something of a cat species, and I would say it is most probably a feral cat, but it is very large, even if it is just a feral cat," Mr Braunton said.

Mr Braunton said it was hard to determine if it was a puma-sized cat from the photo and video, taken from 100 metres away.

"On just the photo alone, mainly with a cat you really notice differences when it is walking, as to a feral animal or a big cat species," he said.

"Unfortunately it is inconclusive, but I think it certainly is a very, very big cat, and Bev would be right in thinking that it is worth photographing."

'I know what I saw'

Ms Fraser told the ABC people might consider her some sort of crazy cat lady, but she stood by her claim.

"This cat had climbed up on a fence post and was sitting on a substantial fence post staring down into the undergrowth," she said.

"It was obviously hunting something, looking and concentrating obviously as cats do. I am now hesitant to go down there."

Mr Braunton said Ms Fraser was courageous in alerting authorities, because others would not through fear of ridicule.

He said the evidence of big cats' existence in Australia was overwhelming.

Another big cat sighting prompts second probe

Details of Ms Fraser's sighting have prompted a man to come forward, with a second and separate sighting of a puma-sized cat around 30 kilometres from her place.

Chris O'Neill saw a cat the size of a puma last Thursday, as he drove home from dinner.

He spoke to DPI investigators today and they said they would do a site visit to look for paw prints or scratch marks tomorrow.

Mr O'Neill said it was a sighting he would never forget.

Chris O'Neill says he saw a big black cat last Thursday, as he drove home from dinner. ( ABC News )

"A black feline cat-like creature, was kind of running under or near a truck and it was the same size as the wheel," Mr O'Neill said.

"So it was a very big creature and its movement was cat-like but it certainly wasn't a domestic cat.

Meanwhile, a second man has told the ABC his brother saw a puma-sized cat leaping into the river last year, within a few hundred metres from Mr O'Neill's sighting.

The alleged sightings of big cats have prompted hundreds of comments on social media.

Dozens of people have said that they too, or someone they know of, have also seen a panther or puma-sized animal in the Hunter Valley region.

Theories have ranged from a breeding pair of pumas escaping from a travelling circus, to an underworld figure releasing a big cat that was once a pet.

Previous big cat sightings dismissed

A report into big cats in NSW was commissioned by former primary industries minister Katrina Hodgkinson and written by New Zealand-based invasive species expert John Parkes.

He found there was no conclusive evidence that large cats existed in the wild in NSW.

The sightings and other evidence presented was mostly from the Hawkesbury region.

The DPI said it would not comment further on the reported Hunter Valley sightings until had completed its investigations.