It comes in a range of different flavours and colours, such as purple for grape, pink for strawberry and so on.

Each tinfoil pack of the drug weighs about 7.7g.

It is said to give an exhilarating effect - similar to that of ecstasy - to those who consume it.

In late May, police raided a Tsuen Wan flat and seized 259 packs - amounting to about 2kg - of the drug.

They believe the drugs were destined for bars and clubs in Mong Kok.

"This drug has flavours and dissolves easily in drinks," said Anna Tsang Yim-sheung, deputy district commander of Mong Kok.

"It's possible that it is used as a date-rape drug in bars or other entertainment venues, although no cases have been reported yet," she said.

Mong Kok district has seen a rise in the number of teenage drug-related crimes, with 21 cases in the first five months of the year compared with 37 in the whole of last year.

In the first five months, there were 11 cases of teenage drug possession, which was the total number of such cases for last year.

Just last month, police arrested a 16-year-old boy who was found carrying 100 grams of the drug Ice. The teenager, who was on his way to Mong Kok from Wong Tai Sin, was detained after he tried to run away when the taxi he was in was stopped at a roadblock.

In early May, officers found 50 grams of ketamine on a 14-year-old boy after he was stopped at Shanghai Street at midnight.

"Teenagers are easily lured by bad friends to earn easy money of about HK$800 to HK$1,000 a time by helping drug smuggling," said Rene Lam Suk-man, district operation officer of Mong Kok.

Over the summer holidays, police will step up patrols in bars, restaurants and other entertainment venues to try to curb teenage drug-related crimes.

A 24-hour hotline - 6148 1205 - has also been set up for teenagers to report any drug-related crimes in the district.