A police spokesman on local residents' reaction

The Metropolitan Police are advising people in Potters Bar and South Mimms not to approach the animal, which is described as "bigger than a Labrador dog" and to keep windows and doors locked.

Police have alerted residents of the area to the possible presence of the "puma-like creature" by using a loud hailer.

Search continues

RSPCA Inspector John Storey: Man is its only threat

The hunt began after two separate sightings of the beast were reported to Barnet police on Friday evening, then two police officers spotted a similar animal in a field on Saturday.

Search teams consisting of police and representatives from London Zoo, the RSPCA and the Royal Veterinary College have so far failed to track the animal down and will continue the search on Sunday.

Unlike the Beast of Bodmin, the Potters Bar Puss is described as being sandy in colour

Curator of Whipsnade Wild Animal Park Nick Lindsay told BBC News Online the cat - described as sandy in colour and having a tail longer than its body with a black ring at the tip - was probably too small to be a puma.

"A puma is considerably larger than a Labrador. If it is a cat, it's more likely to be a lynx or some breed of African wild cat," he said.

Public safety

BBC News 24 talks to local residents and find they think "it's a bit of a joke really"

RSPCA spokeswoman Charlotte Morrissey suggested that if the animal was a big cat, it was probably illegally imported and not part of an "indigenous" population.

"These animals are usually brought into the country illegally by private collectors who then lose them or release them for some reason," she told BBC News Online.

"If somebody lost it, they are unlikely to have reported it because it would lead to prosecution."

The BBC's Mark Edwards reports

Ms Morrissey hoped the animal could be caught alive.

"There are problems associated with catching it live," she said.

"We have to consider the animal's welfare, but the police have to consider public safety."

The RSPCA is in consultation with a London Zoo vet about the best way to capture the creature, if and when it is found. It is thought that a sedative fired from a dart gun is the most likely solution.

'Core of truth'

Cary Johnston reports from Hertforshire: "So far the search has been unsuccessful"

Mr Lindsay said he was "sceptical but fascinated" by big cat sightings in the UK.

"It depends on the individual, but if a big cat had escaped it only has a slim chance of survival," he said.

"Life in a cage is quite different to going out into the big bad world and hunting for yourself. In order for this creature to survive for any length of time, it would have to be part of a breeding population."

He thought that there was probably a "core of truth" to the hundreds of sightings of big cats in the UK - the most famous of which is the Beast of Bodmin Moor - but said even the police could be unreliable witnesses.

"The sightings tend to come in spells, especially if there's just been a programme on TV about it.

"I have a colleague at London Zoo who was called out last year after the police spotted a 'big cat', only to find it was an ordinary ginger moggy," he said.

The RSPCA has already been called out to deal with a number of "exotic" animals this year, including a Cayman crocodile found in Kent in August.

Other big cat sightings in the UK

• In August, the RSPCA confirmed that a paw print found in Lincolnshire was that of a big cat.
  
• In 1995, a Ministry of Agriculture inquiry found no evidence to support the existence of a big cat - the Beast of Bodmin Moor - that was said to be savaging sheep in Cornwall.
  
• Less than a week later, the skull of a big cat was discovered in the River Fowey near St Cleer in Cornwall. The Natural History Museum's Zoology Department concluded it was part of a leopard-skin rug.
  
• Also in 1995, a retired gardener in Dunfermline delivered a video to the Courier newspaper of what appears to be a big cat on waste land near his home. The sighting has not been verified.
  
• Conspiracy theorists claim that after the introduction of the 1976 Dangerous Animals Act, UK collectors released dozens of big cats into the wild, rather than give them up.