Traces of horse meat have been found in burgers on sale in some of the country's busiest supermarkets, food safety chiefs in Ireland have revealed.
Scientific tests on beef products sold in Tesco, Dunnes Stores, Lidl, Aldi and Iceland uncovered low levels of the animal's DNA.
Professor Alan Reilly, chief executive of the Food Safety Authority of Ireland (FSAI), said there was no health risk but also no reasonable explanation for horse meat to be found.
According to the research by the FSAI, one sample of burger goods, Tesco Everyday Value Beef Burgers, showed about 29% horse meat relative to beef content.
"Whilst there is a plausible explanation for the presence of pig DNA in these products due to the fact that meat from different animals is processed in the same meat plants, there is no clear explanation at this time for the presence of horse DNA in products emanating from meat plants that do not use horse meat in their production process," Prof Reilly said.
"In Ireland, it is not in our culture to eat horse meat and therefore, we do not expect to find it in a burger."
The retailers have told food safety chiefs they are removing all implicated products from their shelves. The FSAI said consumers can return implicated products to retailers.
Beef burger products which tested positive for horse DNA were produced by Liffey Meats and Silvercrest Foods in Ireland and one UK plant, Dalepak Hambleton.
The DNA tests found horse in the following products: Tesco Everyday Value Beef Burgers 29.1%; Tesco Beef Quarter Pounders 0.1%; Oakhurst Beef Burgers in Aldi 0.3%; Moordale Quarter Pounders in Lidl 0.1%; Flamehouse Chargrilled Quarter Pounders in Dunnes Stores 0.1%; two varieties of Iceland Quarter Pounders 0.1%.
Tesco said it was treating the incident as extremely serious, Aldi said it was conducting an investigation and Lidl said it has removes all implicated products from sale pending a full investigation.