Neighbours have told of their horror as a huge blaze engulfed farm buildings killing thousands of pigs trapped inside.
Those living near the farm were awoken after 5am by the squeals of stricken animals and large bangs as structures collapsed.
They said the heat from the fire was so intense they feared it would spread to their homes.
The Fire Service said around 3,500 piglets and 800 sows died in the fire, which it initially believed had been started deliberately.
However, it is understood staff at the farm near Bessbrook, Co Armagh, believe an electrical fault may have been to blame, and estimated the number of animals killed at 2,500. A police investigation is under way into the blaze which happened early on Saturday and took seven hours to bring under control.
A woman who lives close to the farm on the Derrywilligan Road, just outside Bessbrook, said frantic neighbours knocked on her door to alert her.
She described the scene which she encountered outside her property as a nightmare.
"It was shocking," the woman, who asked not to be named, told the Belfast Telegraph.
"It was a nightmare; the noise, the smoke and the heat. It was very scary. I've two young boys in the house.
"People were running up and down trying to fight it back, but the firefighters were fantastic."
Another neighbour said he was upset by the sounds of the animals caught up in the tragedy.
"Awful," he said. "The poor animals were squealing but there was nothing anybody could do."
Firefighters used five fire engines and a command support unit to extinguish the flames. Water tankers and a hydraulic platform were also brought in from nearby towns and villages.
Hundreds of animals were saved during the incident.
The devastation caused by the fire was apparent yesterday as staff on the site set about a huge clear-up.
A number of lorries arrived throughout the day to transport dead animals from the area.
Those working at the farm were too distressed to comment.
Yesterday morning the Fire Service said it believed the fire was deliberate, but last night a spokeswoman said that opinion had changed, with the blaze increasingly likely to be accidental.
Police said their inquiries into the cause of the fire were ongoing.
SDLP Newry and Armagh MLA Dominic Bradley said local people in the rural community were stunned by the loss and the "terrible suffering" the animals endured.
DUP MLA William Irwin, who knows the farmer who owns the property, said it was a major blow to the industry.
"Agriculture in general is under pressure with costs of production continuing to rise and a real price squeeze on farmers in the processing and retail end of the scale, so to see this type of loss of animals and property is concerning and unfortunate for the producer concerned," he said.
Ulster Unionist MLA Danny Kennedy said it was vital the cause of the fire be established as quickly as possible.
"This is distressing news of such a huge loss of livestock which will have a very severe impact on the business in the rural area of Bessbrook," he added.