Police have raided a slaughterhouse in West Yorkshire and a meat firm in Aberystwyth as the horsemeat scandal escalates.
Officers were accompanied by food safety officials from the Food Standards Agency (FSA) who were investigating alleged mislabelling of horsemeat sold as beefburgers and kebabs.
Investigators believe that Peter Boddy Licensed Slaughterhouse in Todmorden has supplied horsemeat to Farmbox Meats Ltd in Llandre. It ordered a suspension of operations for both companies.
"This is absolutely shocking. It's totally unacceptable if any business in the UK is defrauding the public by passing off horsemeat as beef," said Environment Secretary Owen Paterson.
"I expect the full force of the law to be brought down on anyone involved in this kind of activity.
"I ordered an audit of all horse-producing abattoirs in the UK after this issue first arose and I was shocked to uncover what appears to be a blatant misleading of consumers," added Andrew Rhodes, the FSA's director of operations.
"I have suspended both plants immediately while investigations continue."
Meanwhile, Waitrose said it withdrawn from sale its Essential British frozen beef meatballs after pork was found in two batches.