Horsemeat scandal: 'we will never know how many have eaten horse' Horsemeat products at horse butchery in Dortmund. Photograph: Ina Fassbender/ Reuters It is unlikely the exact number of people in the UK who have unwittingly eaten horsemeat will ever be known, the chief executive of the Food Standards Agency has conceded. Catherine Brown said that testing was the right way to address the issue, and said the focus would be on areas of higher risk. But she admitted that how many people who had unknowingly eaten horsemeat was likely to be impossible to ascertain. I don't think that we ever will [know how many], because these tests are a snapshot, so even where we find things it is very hard to work out how long, what number of batches, so I think it is unlikely that we will ever know that. It is shocking," she told the BBC. Her comments came as the head of the Hospital Caterers Association said on Saturday that all food suppliers to hospitals would be assessed to trace the sources of their meat products. It emerged on Friday that burgers containing horsemeat have been supplied to hospitals in Northern Ireland. Janice Gillan, chair of the HCA, told BBC Breakfast: "The independent assessor is currently out reassessing all our suppliers at the moment to get real assurances for the public. If anything shows up at all - for example the burgers in Northern Ireland - then they're immediately removed from the premises. Meanwhile, the head of a major UK supermarket chain insisted that the horsemeat scandal was not "the tip of an iceberg." Justin King, chief executive of Sainsbury's, told BBC2's Newsnight that supermarkets had not been slow to react to the scandal, but conceded there was a long way to go before the food industry could fully explain how the crisis has come about. He said last night: "I don't think it's the tip of an iceberg. I think there are some encouraging signs from today's tests that we are starting to get to the bottom of this particular issue. We, in Sainsbury's, have a huge testing programme; we have 50-odd people, whose full-time jobs are to test products. They test raw materials when they come into the factory. The product is delivered to our warehouses and we buy product, as customers do, to test it too. And most of the industry would say something similar. So, we go to great lengths to ensure our food is what we expect it to be. Trust is the core of our businesses. Officials investigating the horsemeat mis-labelling scandal will continue examining evidence on Saturday after three more processing plants were raided. The Food Standards Agency visited two premises in Tottenham, north London, and one in Hull, Yorkshire, on Thursday. Investigators, accompanied by police officers and local authority officials, made seizures at the three sites and removed meat samples for testing. "Computers and documentary evidence have been removed from these premises, as well as meat samples that have been taken for testing," the agency said. The FSA also said it had passed on evidence to Europol - the European Union's law enforcement agency - and the authorities in dozens of countries. It said: "The FSA has submitted a full file and evidence on this issue to Europol. The agency has continued to provide information to Europol, and this information has now been analysed by both Europol and law enforcement agencies in 35 countries - across Europe and elsewhere. Three men who were arrested on Thursday on suspicion of offences under the Fraud Act have been released on bail, Dyfed Powys police said. Dafydd Raw-Rees, 64, the owner of Farmbox Meats near Aberystwyth, and a 42-year-old man were arrested in Wales. A 63-year-old man was also arrested on suspicion of the same offence at Peter Boddy Slaughterhouse in Todmorden, West Yorkshire. The men will return to answer bail in Aberystwyth at a later date, police said.