People are being warned not to eat certain batches of organic free-range chicken from the Northern Ireland producer Moy Park - sold in Tesco, Superquinn and Dunnes, after they were found to contain a banned veterinary medicine.
The chicken is contaminated with nitrofurans - which increases the risk of cancer if there is exposure over a long period, according to a warning posted last night on the website of the British food authorities.
Under EU law it is illegal to use nitrofurans in animals because of the cancer risk.
The problem came to light during routine tests carried out by the Department of Agriculture and Rural Development in Britain, the Food Standards Agency in Britain said.
The Irish Food Safety Authority said last night it was "in contact with the food standards agency in the UK and Moy Park to investigate how the chicken became contaminated and to ensure that it does not occur again", said a spokesman.
The affected batches are: at Tesco supermarkets, chicken or chicken pieces in the range with use-by dates of 10th, 11th, 12th October; at Superquinn, chicken or chicken pieces with a use-by date of 8th, 11th or 12th October; and at Dunnes, chicken or chicken pieces with a use-by date of 8th, 10th, 12th October.
The FSA said while these products will no longer be on the supermarket shelves, consumers should check their freezers for products from these batches, and either discard them or return them to their retailer.
Consumers who may have eaten chicken from these batches "should not be unduly concerned because the increased risk is related to long- term exposure to the drugs," a spokesman said.