It's a banned substance in China, yet it continues to enter the food chain and cause humans to get sick. Clenbuterlo or "lean meat powder" is a drug that some top athletes have illegally used to improve their performances.

The same can be said for Chinese farmers who feed it to slim down pigs and boost their muscle mass. One of the country's leading meat producers stands accused of buying pigs contaminated by the substance and then using the meat in its products. Nick Jones has more on another chilling food safety issue here in China.

Jiyuan Shineway is a subsidy company of Henan Shineway Group, one of the major meat producers in China. They say there are eighteen safety checks, but no test of the chemical clenbuterol. In one pig farm in Wenxian county that supplies pig meat, the pigs ready for slaughter impress people by their fitness and bulk despite some of the animals having trouble standing and walking.

It is learnt from the farmer that these pigs, fed with the chemical clenbuterol, would be sold a week after to Jiyuan Shineway. With minimal testing, the trade is often conducted behind closed doors. According to one pig trader, contaminated pigs from other farms are also sent to Jiyuan Shineway.

A pig trader said, "For Shineway, they claim that they do not collect the chemical clenbuterol-fed pigs. But actually they like buying such pigs. Saying and doing are two different things for them."

The tainted food scandal has been reported on national television and consumers across China are now worried about the quality of the pork they are eating. In Nanjing, capital of east China's Jiangsu Province, where the contaminated pork is claimed to be sold, authorities are conducting a comprehensive investigation.

Sun Liancai, Vice Director of Jiangsu Provincial Bureau of Industry and Commerce, said, "First of all, we should get the questionable products out of the market. Then they are brought to the government-designated department to go through quality check. Once the clenbuterol contaminated products are found, they should be destroyed on the spot."

So far, all the stores of Shineway in the city of Nanjing have been shut down for quality inspection. The result of the investigation will be disclosed to the public as soon as possible. The problematic pork has raised safety concerns nationwide, but people believe it is just the tip of the iceberg.

According to the national regulation issued in 2002, clenbuterol is strongly prohibited in animal feed. Facing the problem of pork contamination, the Ministry of Agriculture will cooperate with other relevant departments to tighten the clenbuterol control and make sure the food people consume is safe.