BANGKOK (Reuters) - Thai authorities Wednesday cracked down on growing commercial sales of a native wonder herb which helps enlarge women's breasts and cures impotent men.

The popularity of Kwao Kruea, the root of a wild plant, has soared since last year after a local herbal specialist publicized its exotic properties.

Thai transvestites consume it widely to enlarge their breasts and impotent men, who cannot afford the expensive Viagra cure, do likewise to boost their libidos.

The herbal specialist believes that the herb does not lead to breast enlargement in men who use it.

But the Thai Food and Drug Administration (FDA) in a surprise raid Wednesday confiscated hundreds of Kwao Kruea tablets and capsules sold at a popular department store in downtown Bangkok.

``Kwao Kruea is not yet registered or approved by the FDA. Distributors of unregistered drugs can face up to two years in jail if courts find them guilty,'' an FDA official told Reuters.

She said several producers of Kwao Kruea medications were not registered and had made exaggerated claims in the advertising of their products which could be misleading for consumers.

``Kwao Kruea has now become a popular herb among transvestites and women with small breasts. This is something which the FDA cannot allow to continue,'' she added