A food manufacturer in Strabane, Co Tyrone, has been named as the supplier of Halal-certified food found to contain traces of pork DNA.
McColgan Quality Foods was identified by the food distributor 3663, which supplied the contaminated beef pies to UK prisons.
3663's contract as a supplier to prisons has been suspended by the British government, after the contamination was discovered.
Islamic law forbids the consumption of pork.
In a statement, McColgan Quality Foods said it was cooperating with the Food Standards Agency and had acted swiftly to identify, isolate and withdraw all of the products in question.
McColgan said that at no point had pork of any kind been included in the recipes of any of the Halal-certified products it supplies.
3663 has said it will not source any further Halal products from McColgan Quality Foods.