Retailers in the United Kingdom and Ireland have recalled an estimated 10 million pounds of hamburger after three beef processors were found to be distributing burger patties that contained horse and pig DNA. Over the weekend, the Irish Food Safety Authority (IFSA) informed news outlets that the horsemeat has since been traced back to an accredited meat supplier in Poland. The IFSA discovered the undeclared horsemeat in 10 out of 27 samples taken from 10 beef processing plants. Those 10 samples containing horsemeat came from three plants: Silvercrest Foods and Liffey Meats in Ireland, and Dalepak Hambleton in the U.K. Of those 27 samples, 23 also tested positive for pork DNA. Burger King has discontinued business with Silvercrest, its burger supplier in the U.K. and Ireland. Most of the samples featured very low amounts of horse DNA, though one sample sold at a Tesco supermarket contained 29 percent horsemeat. Samples that tested positive for horse DNA were also sold at Dunnes Stores, Lidl, Aldi and Iceland supermarkets. The IFSA maintained that while the burgers were not 100 percent beef as advertised, they did not pose a public health threat. Horsemeat is legal to produce and consume in the U.K., though the practice in the U.S. is generally considered a taboo. Most horsemeat intentionally consumed in the U.K. is imported from France. In the U.S., Congress allowed a five-year ban on horse slaughter for human consumption to expire in November 2011. At least one beef slaughterhouse, New Mexico-based Valley Meat, has applied for equine meat inspection services from the U.S. Department of Agriculture.