Arrests have tripled since last year in an operation against youth crime carried out by Mong Kok police, but the authorities say the crime rate has not increased.
Between mid-July and the end of August, 135 people were arrested in the operation. There were 37 arrests last year.
Of the arrests, 82 involved drug offences. Nine of those arrested were aged under 21 - and the youngest was 15.
Police seized more than 2kg of illegal drugs worth HK$660,000. The drugs included 1.7kg of ketamine and some cocaine.
Jack Mok Tsz-wai, officer in charge of the district intelligence squad, said the increased number of arrests did not mean a rise in the youth crime rates in the district. The number of youth crimes in the first eight months in fact fell 30 per cent to 129 from 182 last year, he said.
"We have stepped up patrols in a variety of venues, including hotels, internet cafes, bars and clubs, which explains the jump in the number of arrests," said district operation officer Rene Lam Suk-man.
But the youngsters' involvement in drug offences still warrants close attention.
Police statistics showed the number of drug-related youth crimes in the first eight months rose to 27 from 22 last year.
In the recent operation, police arrested a 17-year-old female student in a Tai Kok Tsui flat for possession of drugs after they found 66 grams of Ice in her purse. She claimed she was helping her friend deliver the drugs for a payment of HK$200.
Lam said the police were seeing many young people becoming involved in drug offences in their attempts to make a quick buck during the school holidays. Payment for delivering drugs could earn them as much as several thousand dollars, she said.