In the latest mainland food scare, tonnes of pig blood curd, a favourite food in Chongqing, have been found soaked in carcinogenic formalin to preserve freshness. Inspectors from the Jiulongpo district industry and commerce bureau found nearly five tonnes of suspected contaminated blood curd in a 4am raid yesterday on a workshop at Baishiyi, said China News Service. The workshop began making blood curd two years ago, despite not having business or hygiene licences. It supplied blood curd to markets in Xiaolongkan, Panxi and Lieshimu in Chongqing. Formalin, a liquid containing 35 per cent to 40 per cent formaldehyde, is used as a disinfectant and for preserving biological specimens. It has been banned as a food additive because it can cause cancer and deformities in newborns. 'Some blood curd inspections showed more than 100 milligrams of formaldehyde in each kilogram,' one inspector told the news agency. As little as 1 milligram of formaldehyde per litre is thought to put people at risk. This follows reports this week that Clenbuterol, known on the mainland as 'lean meat powder', was being fed to pigs to reduce body fat and give meat a pinker, fresher appearance. Eating tainted meat may cause dizziness, fatigue, palpitations and other medical conditions. The Henan government has ordered 16 farms to stop selling pigs. Some supermarkets have removed products made by processed-meat giant Shuanghui from shelves in Beijing, Shanghai, Shenzhen and Nanjing after reports that it used Clenbuterol-tainted pork, China Central Television's website reported. The Chongqing industry and commerce bureau has closed down the 200 square metre blood curd workshop. On the floor, which was covered in muddy water, were two dozen uncovered metal boxes filled with half-made blood curd. Three concrete-walled steaming areas were filled with processed blood curd and 10 large plastic buckets contained blood curd ready for shipping. A worker said pigs' blood was bought from slaughterhouses in the Shapingba district. It was then solidified by adding salt and water before the semi-solid blood curd was soaked in formalin. Blood curd - xuewang in Putonghua - is made of ducks' or pigs' blood and is usually cooked with peppers and oil.