A food processing plant in Leeming Bar, north of Ripon, is one of the factories at the centre of an investigation tracing horse meat found in Tesco beef burgers.
Tesco has now removed thousands of beef burgers from its stores after tests revealed some of them contained horsemeat.
Horsemeat products have been traced to a North Yorkshire plant run by Dalepak, at Leeming Bar.
Tests carried out by the Food Safety Authority of Ireland revealed traces of horse DNA in burgers made at the Leeming Bar plant, in addition to two factories in Ireland.
Horsemeat accounted for about 29 per cent of the meat content in one frozen beef burger sample from the supermarket giant.
In another nine samples of beef products from the three plants, horse DNA only accounted for a small percentage relative to beef content.
All the retailers said they are removing all implicated products from their shelves.
The DNA tests found horse in the following products: Tesco Everyday Value Beef Burgers 29.1 per cent; Tesco Beef Quarter Pounders 0.1 per cent; Oakhurst Beef Burgers in Aldi 0.3 per cent; Moordale Quarter Pounders in Lidl 0.1 per cent; Flamehouse Chargrilled Quarter Pounders in Dunnes Stores 0.1 per cent; two varieties of Iceland Quarter Pounders 0.1 per cent.
In a statement, Tesco Group’s technical director, Tim Smith, said: “We are working with the authorities in Ireland and the UK, and 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 the investigation.
“We understand that many of our customers will be concerned by this news, and we apologise sincerely for any distress.”
The Irish government have now ordered a full investigation.
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 it to be found.
“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,” he said.
The FSAI analysed 27 beef burger products with best before dates from last June to March 2014 with 10 of the 27 products – 37 per cent – testing positive for horse DNA and 85 per cent testing positive for pig DNA.
Some 31 beef meal products such as cottage pie, beef curry pie and lasagne were tested with 21 found to be positive for pig DNA. All tested negative for horsemeat.
The FSAI analysis also found traces of horse DNA in batches of raw ingredients, including some imported from the Netherlands and Spain.
Lidl supermarket have now confirmed they will refund any products customers fear have been affected.
Aldi said: “We have sought information from one supplier, Silvercrest, which is dealing directly with the FSAI on the issue that has been raised.”