Hong Kong's big store chains stripped their shelves of Mengniu milk yesterday despite government tests showing its products were free of melamine and the firm's claim that its milk came from safer farms. Wellcome and ParknShop recalled the Hong Kong-listed company's products within 20 hours of the mainland authorities revealing that milk, not just milk powder, produced by Mengniu and other leading companies for sale on the mainland was adulterated with melamine, an industrial chemical. More than 6,200 children on the mainland have developed kidney stones, and four have died, after being fed adulterated baby formula. More than 150 have suffered acute renal failure. Hours after stores began clearing their shelves, the Centre for Food Safety said tests on samples of 36 Mengniu products - and 11 other dairy items from the mainland - sold in the city had found no melamine. Mengniu, the country's largest milk supplier, said its exported products, including those for Hong Kong, were less likely to be contaminated. Wellcome and ParknShop said they removed the products from shelves as a precaution. Jusco Department Store and the Yu Kee grocery chain removed all Yili Dairy and Mengniu Group products on Tuesday. Nissin Foods Company withdrew a boxed dessert, Retort Pouch Cha Cha, made using a Yili milk product, and the Centre for Food Safety said it would collect samples and appealed to people who had bought the dessert not to eat it. Asked why the government had not urged a recall of all Mengniu products and whether it was reacting too slowly, Food and Environmental Hygiene Department director Cheuk Wing-hing said that legally it could only ask for tainted goods to be removed. Secretary for Food and Health York Chow Yat-ngok said he respected the retailers' decision to remove all Mengniu products. He said the government had taken immediate steps to test milk and other dairy products as soon as the melamine adulteration came to light. He said the government planned to introduce legislation in a few weeks to prohibit inappropriate levels of melamine in food and was studying international practices to set a standard applicable locally. 'Melamine should not be in food at all. It is a substance to adulterate the testing for protein, and it should not be an added ingredient in food. '[When] you look at guidelines from the European Parliament on food safety, they added a certain clause on migratory elements. Sometimes packages used to contain food might have melamine and can contaminate the food itself. It is something we should look at.' Pointing out that the government only discovered that some foods were dangerous when problems arose, the Democratic Party's consumer affairs spokesman, Fred Li Wah-ming, asked how it could ensure food sold in Hong Kong was safe. 'We cannot predict which of the many chemicals will be found in food products,' Dr Chow said. The Centre for Food Safety monitored news media every day for reports about food safety, he said. The government could test at most 60 samples daily, he said. It would extend tests to include more products with dairy ingredients. More results would be available in the coming days, he said. Legislators including Ip Kwok-him of the Democratic Alliance for the Betterment and Progress of Hong Kong and the Civic Party's Audrey Eu Yuet-mee expressed concern about milk powder supplies in the city after mainlanders had rushed across the border to buy it. Manufacturer Wyeth said its supply remained stable despite sales of milk powder in some pharmacies in the New Territories having risen by 40 per cent. Yata Department Store (formerly Seiyu) confirmed it had enough stock even though demand for Japanese milk powder increased by about 10 per cent this week.