Farmers who supply the Glanbia-owned plant with about 10,000 pigs a week — about 20% of the national kill — voiced concern about finding alternative buyers as the news came through.

The site was not operating when the fire broke out at about 6am and there were no injuries. Fire service units from Co Offaly fought the blaze and brought it under control.

Glanbia said while the precise cause of the fire is not yet known, the incident is being investigated by the company, which has another pig processing plant in Roscrea, Co Tipperary.

“Damage is being assessed and early indications suggest the plant may not return to production for some time,” it said.

The company said it is working on an immediate contingency plan in relation to employees, customers and suppliers.

Glanbia Meats chief executive Jim Hanley said the company, regrettably, had to issue protective notice to its staff.

“We are very conscious of the impact the fire has on employees, their families and the local community and we are doing as much as we can.

“We are confident of returning our management and staff to employment as soon as possible,” he said, confirming that the company will be meeting with all staff this morning.