It was confirmed that 75 per cent of equine DNA had been found, in raw ingredients at Rangeland Foods in Co Monaghan, just days after the ABP Food Group lost an estimated €45 million (£38 million) over the scandal.
Irish police have been called to aid inquiries, with a special team from the Department of Agriculture tasked to investigate.
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The Office for National Statistics said gross domestic product grew by just 0.1%.
William's comments came during a surprise appearance at an event scheduled for just his brother.
Matt Campbell, who collapsed just a few miles from the finish line, had hoped to raise £2,500.