A toxin linked to the seals on bottles and jars has been found in a range of foods from baby food to tomato ketchup. The discovery has thrown the food industry into turmoil and triggered an urgent investigation in Britain and Europe. The problem was first identified by food firm Nestle and other rivals. Now a group of manufacturers, including Heinz, has launched an investigation. The substance involved is a semi-carbazide or SEM, which has not been extensively tested for toxic effects. But animal studies have linked the substance to cancers, liver damage and, at high doses, miscarriage and birth defects. The problem was revealed by the EU Food Safety Authority, which has been alerted by the industry within the last few weeks.