Both Silvercrest and Rangeland have suspended operations. Silvercrest already has lost its major supply contracts with Tesco and Burger King.
Alan Reilly, chief executive of the Food Safety Authority, said the latest findings demonstrated that Ireland was dealing with fraud, not an accidental contamination.
"We're no longer talking about trace amounts of horse DNA in product. We're talking about horsemeat. Somebody, someplace, is drip-feeding horsemeat into the burger manufacturing industry. We don't know yet exactly where this is happening. All the documentary checks that we have on these shipments show that they have come from Poland," Reilly said.
Reilly chided Polish veterinary authorities for failing to tell Ireland about any of the official results of their investigations there.
But Susan O'Keeffe, an Irish senator whose work as an investigative journalist two decades ago blew the lid on corrupt practices among Irish beef exporters, said the paper trail could not be trusted to identify the horsemeat fraudsters. She noted that Irish producers two decades ago were caught mislabeling meat for a range of scams, including the sale of rotten beef hearts to Russia and non-halal meat to Muslim countries.
"People were employed to cut, scrape labels off frozen meat, and put their own stamps on it," O'Keeffe said. "You could do it with the meat itself, and you could do it with the box. You could forge labels. You could write your own labels. You could print your own labels. All of this did happen in our time."
O'Keeffe said Ireland therefore could not trust its conclusions now to labels and papers that could be forged or altered. "It doesn't naturally follow that the meat came from Poland or that the meat was Polish," she said. "It might be. But it may not be."
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