A total of 27 frozen beef burger products were analysed by the Food Safety Authority of Ireland and 10 of them, or 37%, tested positive for horse DNA.
The FSAI said the meat came from two Irish processing plants, Liffey Meats and Silvercrest Foods, and one in the UK - Dalepak Hambleton.
It was on sale in Tesco, Dunnes Stores, Lidl, Aldi and Iceland.
Professor Alan Reilly of the Food Safety Authority said the horsemeat poses no risk to public health but does raise concerns.
"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 explained. "Consumers who have purchased any of the implicated products can return them to their retailer.
In Ireland, it is not in our culture to eat horsemeat and therefore, we do not expect to find it in a burger.
Prof. Alan Reilly , FSAI
The survey uncovered low levels of the DNA in most products. However it shows that the Tesco's Everyday Value Beef Burgers, which were tested by the FSAI, contained over 29% of horse meat. They were also tested positive for pig meat.
In a statement, Tesco said it apologises for any distress the findings have caused consumers.
"We immediately withdrew from sale all products from the supplier in question," said Tim Smith, Group Technical Director.
"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. We understand that many of our customers will be concerned by this news, and we apologise sincerely for any distress."
Lidl said it has removed all the products from its shelves and is offering refunds, while Aldi is to conduct an investigation into the issue.
The Irish Farmers' Association described the findings as "unacceptable" and said they will be concerning for farmers across the country.
"While the presence of other meats in the frozen burgers was at extremely low levels in almost all of the samples collected, it is unacceptable and the Department of Agriculture must urgently investigate how this might have happened," said John Bryan, IFA president.
"Nothing or no-one can be allowed compromise the high standards and reputation of Irish-produced food."