British supermarket chain Tesco has cleared its shelves of its own brand "beef" burgers. They're not a health hazard but they were found to contain horse meat or traces of it - something that's not socially acceptable in the UK. They were one of five major supermarket chains affected, including Aldi. Three meat factories are now at the centre of an investigation - one in Ireland two in England. In most cases, levels were low but one Tesco's sample contained almost a third horse meat.