BEIJING, July 9 (Reuters) China is looking into claims of a herbal weight loss patch which its makers said helped former US President Bill Clinton's daughter, Chelsea, shed 12 kg in under a month, state media reported today.

Customers are instructed to stick the patch to the area of the body where they want to lose weight and then just wait for the fat to flow out of them, the Beijing Morning Post said, citing an investigation by China Cental Television.

But in fact the oil seeped from the patch itself, which could be seen when it was put on a warmed up cup or a television set, the report said.

The patch is named after an acupuncture point and translates clumsily into ''America Seven-Point Thinness''.

Though it claimed to be imported from the United States -- where the advertisments said it was a top seller and used by Chelsea Clinton -- it was actually made by a company from the nearby industrial city of Tianjin, the newspaper said.

In the few months it was on the market, the commercials helped propel sales to more than 200 million yuan (26.32 million dollars), it added.

''The reporter asked related medical experts, and it is currently generally accepted the most effective way to lose weight is to exercise and rationally control what you eat and drink,'' the newspaper said.

China is trying to crack down on substandard and fake food, drugs, toys and health products after a series of scandals has shaken faith in the ''made in China'' label worldwide.

Health foods and tonics are particularly popular, often claiming to contain special medical herbs which can help with everything from baldness and impotence to lack of concentration.

Reuters SKB DB1040