A company selling ultraviolet light bulbs that it claims can prevent Sars is being investigated by a government department.
Treasure Dream, the Hong Kong distributor of Bright Starlight and Electricity, a mainland firm, has been selling the bulbs for $328.
It claims that one 15-watt UV-C bulb can kill 99.9 per cent of bacteria in a 200 sq ft room for a whole day if left on for one hour.
Advertisements for the bulbs have appeared in the Chinese-language Sudden Weekly magazine and Oriental Daily newspaper.
The bulbs carry a label warning that no one should be present when the light is on, to prevent damage to the eyes and skin.
The Electrical and Mechanical Services Department has told Treasure Dream to stop selling the bulbs for domestic use until it has carried out tests to see if they meet safety standards.