The food in some Guizhou restaurants was just a bit too good. Some would even say it was addictive - and they may have been right. A crackdown by the provincial drug control unit has seen more than 200 restaurants in Guizhou ordered to close after they were discovered spiking their dishes with opium poppies. Police found nearly 10 per cent of 2,640 restaurants inspected were putting opium-poppy shell or seed in dishes ranging from beef noodles to hotpot and spicy snacks. 'We have received numerous reports lately on the illegal use of poppy shell in restaurants. Such tip-offs triggered the investigation,' said Zhang Xing , an official with the provincial drug control unit. Xinhua reported that police seized 3.2kg of poppy seed and 1.7kg of poppy shell. A total of 215 restaurants were ordered to shut. Warnings were issued to a further 36 restaurants. 'Local people have long been under the misconception that poppy shells can make their dishes more delicious. They are not aware of the harm they will do to their health,' Mr Zhang said. Opium-poppy shells and seeds are easily accessible in Guizhou and other border areas such as Yunnan due to their proximity to the Golden Triangle. Cooked with food, poppy shells produce an appealing aroma. Wei Tao , a researcher with the Centre for Disease Control and Prevention in Guizhou, said eating opium poppies was harmful to people's health. 'Opium poppies can cause harm to one's heart and liver. People could get addicted after eating them for a long time,' he said. Investigators found a high concentration of morphine in some of the food samples, Mr Wei said. The drug is obtained from the juice of unripe opium-poppy seed pods. In 1987, officials found one-quarter of the 268 hotpot restaurants inspected in Sichuan province used opium-poppy shell in their food.