POLICE are reviewing drug arrest and seizure figures from the past few years to identify abuse black spots. Initial indications, yet to be confirmed, show Kwun Tong and Tuen Mun are most prone to drug-related activity, Narcotics Bureau commander, Chief Superintendent Iain Grant, said. He was concerned particularly about youth drug-related crime. Mr Grant said it was hoped to collect all empirical data on narcotics so police resources could be better targeted, and to produce a breakdown of figures into age groups and major supply and distribution channels. ''What we are trying to do is look at where the majority of drug abuse takes place,'' he said. ''We may be able to identify supply patterns and that may give us some new areas to focus on. We have a major focus on suppliers . . . our response will be ruthless.'' Police Commissioner Eddie Hui Ki-on recently directed force commanders to place renewed attention on narcotics, especially in the growing youth market, in the wake of a near doubling in seizures of heroin and cannabis this year. Latest half-yearly figures show drug-related arrests reached 7,618 - 22 per cent more than last year's figure. Serious narcotics cases topped 2,000, almost a third more than for the corresponding period in 1993. This includes the seizure of more than 300 kilograms of heroin, compared with 223 kilograms seized off the streets for the whole of last year. ''We are probably looking at the possibility of 450 kilograms of heroin this year,'' Mr Grant said. In the first quarter, 20 per cent of all people arrested for heroin, cannabis and synthetic drug offences were aged 21 or under, and 38 per cent of those arrested for cannabis crimes were youngsters. ''There is a definite increase in youngsters - and we are worried about it,'' Mr Grant said. His concerns were underlined yesterday when Chai Wan police said a new drug had entered the district. Roche 15, a blue tranquilliser pill legally available only by prescription, is taken with heroin to prolong the effect of the narcotic and increase the ''high'' feeling. Deputy divisional commander of Eastern District, Senior Superintendent Gilbert Jorge, said yesterday the pills were ''a recent phenomenon'' and were worrying. ''It is only in the last year that they have appeared,'' he said. Mr Jorge said that between January and July, 1,636 Roche 15 pills were seized along with 3.49 kilograms of heroin. Although figures were not available for the same period last year, the number of pills seized had been minimal. In Mongkok yesterday, detectives arrested six people, and seized a loaded pistol and about 900 grams of heroin worth $350,000. The arrests and seizure were made after three teams of 15 officers wearing bullet-proof vests raided a ninth-floor room in the Copenhagen Hotel in Portland Street at about 12.45 pm. The men were arrested and 18 packets of heroin were found in the ceiling of the toilet. A Chinese-made semi-automatic pistol loaded with seven rounds of ammunition was found in the ceiling outside the room and another 350 grams of heroin was seized from the ceiling in the eighth-floor corridor.