Inspectors from Guangdong administration of quality and technology supervision seal up a batch of suspect oil in Zhongshan, Guangdong province, on May 16. [Photo/Xinhua]

Inspectors test the cooking oil at a restaurant in Boxing county, Binzhou city, Shandong province, on May 14. [Photo/Xinhua]

Another 10 tons of suspect oil needs to be recalled from the market in southwestern China's Yunnan province, according to a source from a local oil manufacturer that was believed to be adding industrial animal fat to edible oil products.

Zhang Yingyu, deputy general manager of the company, told China Daily on Wednesday it was possible that the problem occurred during the purchasing of raw materials.

"We bought the suspected lard and fish oil from a supplier in Guangdong province and we had found nothing wrong with it in the past," said Zhang, adding the supplier had cooperated with his company for nearly two years.

An initial investigation revealed that Yunnan Fengrui Oil and Fat Company was suspected of producing three types of cooking oil with animal fat that is only supposed to be used for industrial purposes, according to a news conference jointly held on Tuesday by three government departments, including the Yunnan bureau of quality and technical supervision.

The use of industrial animal fat in the production of food products is prohibited, as it cannot meet the hygienic standards required for cooking oil and contains high levels of chemical pollutants such as paraffin, said Dong Jinshi, executive vice-president of the International Food Packaging Association in Beijing.

Industrial animal fat is mainly used to make soap, he added.

Wang Ruiyuan, vice-chairman of the oil branch of the Chinese Cereals and Oils Association, said Fengrui has been known to be producing lard.

Animal oil for cooking should meet higher quality standards than that for industrial production, and people can tell the difference between the two from their color and smell, Wang said.

Liu Yunfeng, the head of the division of food production supervision of Yunnan provincial bureau of quality and technical supervision, told the news conference that the food safety authorities had investigated thousands of local markets and restaurants, and had asked the oil company to recall more than 136 tons of inferior oil by late on Monday.

"We have suspended all oil production and set up more than 20 offices across the province to recall suspect oil," said Zhang from Fengrui.

Official food quality inspectors will be deployed to supervise the entire recall process, according to a statement released during the news conference. The food safety watchdog in Yunnan province also planned to investigate all cooking oil in the province, the statement said.

To encourage public supervision of food safety, the provincial office of the food safety committee will speed up enacting regulations to provide rewards for whistleblowers, it said.

Contact the writers at hedan@chinadaily.com.cn, and guoanfei@chinadaily.com.cn