TESCO, Scotland's largest supermarket chain, has withdrawn all own-brand beef burgers from all stores in the UK and Ireland after horse DNA was found in some being sold in supermarkets.

The world's third-largest retailer, with nearly 200 stores in Scotland and 3000 across the UK, took the action last night with immediate effect "as a precautionary measure only" after the Republic of Ireland's food safety authority (FSAI) discovered the tainted burgers.The burgers were on sale in Tesco and Iceland in the UK and Ireland. In the Republic of Ireland they were on sale in Dunnes Stores, Lidl and Aldi.

The FSAI said the meat came from two processing plants in Ireland – Liffey Meats and Silvercrest Foods – and the Dalepak Hambleton plant in Yorkshire.

It said they posed no health risk.

Iceland which has 780 stores in the UK said they had withdrawn two own brand quarter-pounder burger lines from sale across the UK in response.

A Tesco spokeswoman said: "We have withdrawn all of our own brand Tesco burgers across the UK and Ireland, as a precaution, because we think it is important we get a sense of how this has got into the supply chain."

Tim Smith, Tesco group technical director, added: "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."

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

Horsemeat accounted for approximately 29% of the meat content in one sample from Tesco.