An investigation by food safety officials is underway to discover how beefburgers contaminated with horsemeat were sold in supermarkets including Tesco, Iceland and Aldi.

Tesco and Iceland sold the burgers in the UK while Dunnes Stores, Lidl and Aldi sold the meat in Ireland, where the Food Safety Authority of Ireland (FSAI) discovered that the burgers contained horsemeat DNA.

The meat had come from two processing plants in the Irish Republic - Liffey Meats and Silvercrest Foods - and the Dalepak Hambleton plant in North Yorkshire. Officials said there was no human health risk and the burgers had been removed.

A total of 27 burger products were studied, with 10 of them containing traces of horse DNA and 23 containing pig DNA.

All of the retailers involved have withdrawn the products. Tesco said it is working to ensure it doesn’t happen again.

Raymond Ellard, director of consumer protection at the FSAI, said several investigations will now take place into food safety.

He said: “The companies have taken a very responsible attitude. On a voluntary basis they have withdrawn products from sale, so have the retailers.

FSAI chief executive Professor Alan Reilly said: “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.”

An Iceland spokesman said: “Pending further investigation, Iceland has withdrawn from sale the two Iceland brand quarter pounder burger lines implicated in the study.

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