Guangdong health authorities have advised people not to eat string beans or hyacinth beans after more than 10 people were taken ill. 'We are telling people to avoid eating the beans. Otherwise, they have to make sure they cook them at 80 degrees Celsius to destroy the toxins,' Feng Shaomin , a health department spokesman, said. Dr Feng said those who fell sick had complained of headaches, breaking out in cold sweats, general numbness and vomiting. He said experts did not think the problem was caused by pesticides. 'We think it's because of soil and water pollution. This is an imported variety. It is possible that it is not suitable for cultivation in Guangdong. 'We don't know how the toxins affect people. We don't know where the toxins are coming from. We think it's the red cell agglutinin and saponin toxins in the beans that are causing the problem. We are still investigating,' he said. Following several poisoning cases in canteens in Shenzhen, Guangzhou, Foshan, Maoming and other cities, the department issued a circular over the weekend advising caterers not to serve the beans because some pods might not be cooked well enough when they are prepared in a big wok for mass consumption. Guangdong people prefer their vegetables lightly cooked so they retain their colour and crispness. Guangdong officials were not able to say if the beans were exported to Hong Kong but Guangzhou Agricultural Development, the biggest vegetables supplier to ParknShop in Hong Kong, said it did not grow beans or squash on its farms. A State Environmental Protection Administration survey last month found that 40 per cent of agricultural land in the Pearl River Delta had heavy metal contamination that exceeded safe levels.