Customs officers have arrested three women on suspicion of using counterfeit devices to offer bogus treatments at beauty parlours, violating trade description laws.

The suspects, aged 36 to 40, include the directors of two different parlours in Shek Mun and Kwun Tong.

Acting on intelligence, undercover officers were sent to the parlours in recent days posing as customers, Customs inspector Kan Tsz-him said.

He said the treatment involves a device using High-Intensity Focused Ultrasound (HIFU), and that improper use may cause skin burns.

HIFU targets ultrasound energy to the skin in a process marketed as an alternative to a facelift.

Kan said the authentic device is different from the ones seized in the operation in terms of the way they give out energy.

"According to the sales agent of the authentic device, it involves a non-intrusive method in the treatment without hurting the skin. According to our investigation, the goods seized may not have this function, so there could be an adverse effect," he told reporters.

Kan urged customers to be on the lookout for bogus treatments, saying procedures using authentic devices cost several thousand dollars, several times more than the bogus ones.

All three suspects have been released on bail pending further investigation.