The dogs rescued earlier are being cared for by the USPCA

The discovery was made on Monday at an isolated farmhouse on the Katesbridge Road about a mile from the village of Kinallen in south Down.

It is the third find of its kind in the area in the past five days.

The USPCA and police operation followed the discovery of two suspected illegal puppy farms in the same area last week.

Stephen Philpott of the USPCA said he believed the latest search had uncovered an illegal breeding and training operation for pit-bull type fighting dogs.

"There's equipment in here for training dogs for fighting and there are other pieces of evidence here which we believe was causing unnecessary suffering to animals," he said.

There's equipment in here for training dogs for fighting and there are other pieces of evidence here which we believe was causing unnecessary suffering to animals Stephen Philpott

"There's a large number of these dogs involved, more than a dozen, which are now being removed by the USPCA."

Last week, four pit-bull terriers were among more than 150 dogs rescued. The authorities believe all the finds were linked.

Animal welfare officials said some of the dogs rescued earlier from a farm in County Down had never seen daylight.

More than 100 animals seized near Katesbridge last week are being cared for by the USPCA.

Speaking about the dogs recovered last week, Mr Philpott said the conditions the animals were being kept in were "overcrowded and inadequate".

"Having had time to examine some of the animals we reckon some had been there up to a year," he said.

He said that the conditions the animals were found in were "distressing".

"We believe some of these animals have never seen daylight," he said.

Mr Philpott said one man had recognised a dog from a BBC News television broadcast, which he claimed had been stolen in October.

One of the pit-bull terriers rescued by the USPCA and police

"When he discovered his dog here yesterday (Sunday) it recognised him immediately. It was one of the best moments in my 12 years in the USPCA," he said.

He said that they had been swamped by offers from the public to give the dogs a home, but at the moment the animals were in a "legal limbo".

"We don't know who owns them, we don't know how they came to be there and I have to talk to the other agencies to try to take this forward," he said.