(American College of Physicians) -- Two herbal weight-loss products manufactured in China and sold in Japan and on the Internet caused liver injury to 12 patients taking the product, according to a new study.

One patient died and another needed a liver transplant; the remaining patients recovered after stopping the products, Chaso and Onshido.

Both were advertised by their manufacturers as containing only botanicals, but were found to contain N-nitroso-fenfluramine, a relative of the drug fenfluramine that was taken off the market in the United States after it was linked to heart problems.

The authors caution that consumers and health professionals should be aware that so-called herbal supplements for weight loss may be harmful.