Police have detained 32 people for reprocessing and selling tonnes of used cooking oil, the Ministry of Public Security said yesterday, in the latest food scandal to hit the mainland. More than 100 tonnes of the 'gutter oil', taken from restaurant kitchen waste, was seized in raids that foiled a criminal network operating in 14 provinces, including Zhejiang, Henan, Shandong and Jiangsu, the ministry said on its website. Two production lines and six underground factories were found to be reprocessing and selling the oil. The ministry statement said tests indicated that the confiscated oil contained several kinds of toxins, some of which could cause cancer. 'Not only did we destroy a criminal chain that was illegally turning gutter oil into food oil, we also unveiled the greed of the criminals and pulled back the curtain on the immoral acts of those producing this poisonous and harmful food oil,' it said. The bust added to an already long list of food scandals, including eggs coloured with industrial dye, pigs fed with chemicals to make them leaner, and expired steamed buns dyed with industrial colouring. Three years ago, milk and infant formula laced with an industrial chemical called melamine killed at least six children and made more than 300,000 ill. The scandals have rocked people's faith in not only the mainland's food industry but also the government, with most respondents in a survey in January blaming the government for not doing its job. The survey was conducted by Insight China magazine and Tsinghua University's Media Survey Lab. A food-safety law was passed in 2009, but the scandals have shown no sign of ending. Last year, the State Council said businesses caught using recycled oil would be forced to close temporarily or lose their business licence and that pedlars selling the oil could be prosecuted. Restaurants that use recycled kitchen oil as cooking oil can be fined up to 100,000 yuan (HK$122,000). The ministry said the investigation began with a tip-off in March that a group of people was collecting used oil at a restaurant in Ningbo, Zhejiang. The group told police that they sold the oil to clients in Jiangsu and Shandong, who asked them to test its acidity, a practice needed only when reprocessing cooking oil. Police later found an energy firm in Jinan, Shandong, which was supposed to turn kitchen oil into fuel, was selling it as fresh cooking fat. It bought the roughly refined gutter oil at 5,500 yuan to 6,000 yuan a tonne, reprocessed it and sold it for 8,100 yuan to 8,300 yuan a tonne to wholesalers, who in turn sold it at markets. The ministry had food analysts test the confiscated oil for cancer-causing chemicals after the oil passed standards for colour and acidity.