Food safety authorities are investigating how beef burgers from some of the UK‘s leading supermarkets were contaminated with horse and pig DNA, it has been announced.

The Food Safety Authority of Ireland (FSAI) has published a study following the analysis of beef burger products sold in supermarkets which found that 37 per cent of 27 tested products tested positive for horse DNA while 85 per cent were found to contain pig DNA.

According to the FSAI, the meat was produced by processing plants Liffey Meats and Silvercrest Foods in Ireland and the Dalepak Hambleton plant in the UK and was available in Tesco, Dunnes Stores, Lidl, Aldi and Iceland.

Alan Reilly, CEO of the FSAI, said that, while the news may cause concern, the products do not pose a health risk to the public, though he did accept that some may find the presence of pig traces “unacceptable” for religious reasons.

He explained: “The products we have identified as containing horse DNA and/or pig DNA do not pose any food safety risk and consumers should not be worried.

“Consumers who have purchased any of the implicated products can return them to their retailer.

“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 horsemeat in their production process.

“In Ireland, it is not in our culture to eat horsemeat and therefore, we do not expect to find it in a burger.

“We are working with the meat processing plants and the Department of Agriculture, Fisheries and the Marine to find out how horse DNA could have found its way into these products.”

While grocers Tesco and Iceland sold the burgers in the UK , discounters Aldi and Lidl as well as Dunnes Stores sold the meat in Ireland, though the FSAI noted that “nine of the ten beef burger samples from these retailers, horse DNA was found at very low levels.”

However, one sample from Tesco, which yesterday was reported to have maintained its grocery market share of 30 per cent, was found to contain 29 per cent horsemeat, a discovery which forced the retailer to remove all products from the relevant supplier yesterday.

In a statement, Tesco‘s Group Technical Director Tim Smith said: “We immediately withdrew from sale all products from the supplier in question.

“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.

“We will not take any products from this site until the conclusion and satisfactory resolution of an investigation.

“The safety and quality of our food is of the highest importance to Tesco. We will not tolerate any compromise in the quality of the food we sell.

“The presence of illegal meat in our products is extremely serious.

“Our customers have the right to expect that food they buy is produced to the highest standards.”

Iceland also expressed “concern” over the news and has withdrawn the two Iceland brand quarter pounder burgers pending further investigation.

A statement from the retailer said: “Iceland will be working closely with its suppliers to investigate this issue and to ensure that all Iceland brand products meet the high standards of quality and integrity that we specify and which our customers are entitled to expect.”