Food safety monitors in Ireland have reported that horse meat mixed with beef products is being sold in some of the country's busiest supermarkets.
Horse DNA was found during scientific testing on beef products sold at Tesco, Dunnes Stores, LIdl, Aldi and Iceland, according to the Press Association.
Researchers from the Food Service Authority of Ireland (FSAI), who analysed 27 different beef products, found that over 29 percent of a Tesco Everyday Value Beef Burger was horse meat. Trace amounts were also present in products such as Lidl's Moordale Quarter Pounder, Dunnes' Flamehouse Chargrilled Quarter Pounders and Iceland's own-brand Quarter Pounders.
The research team also found that 85 percent of the beef products tested contained pig DNA.
There is, as yet, no reasonable explanation for the traces of horse meat but Professor Alan Reilly, the chief executive of the FSAI, has confirmed there is no immediate health risk.
"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," the professor was quoted in the Irish Independent.
Reilly added that the presence of pig DNA would be particularly offensive to "some religious groups or people who abstain from eating pig meat", and said that "in Ireland, it is not in our culture to eat horse meat and therefore, we do not expect to find it in a burger."
All contaminated products have been taken off the shelves and consumers have been asked to return purchased products to respective retailers.
The concerned companies have confirmed investigations into the situation.
Tesco reported: "We are working with the authorities in Ireland and the UK, and with the supplier concerned, to urgently understand how this has happened and how to ensure it does not happen again."
Likewise, Aldi and Lidl have also confirmed that appropriate action will be taken and that they have removed all contaminated products from sale.