Three schoolboys aged 14 and 15 were arrested on suspicion of snorting ketamine yesterday after they fell ill in a park in Tin Shui Wai. Police later arrested a schoolmate for allegedly selling them the drug. The three boys, Form Two pupils at Pak Kau College, were found by a security guard in the park behind Yat Chi House, Tin Yat Estate, in Tin Sau Road, shortly before 11.30am. The female guard told police one of the boys was unconscious on the ground and the two others were sitting dazed on a bench. Another boy passed out before paramedics arrived. All were in uniform. They were taken to Tuen Mun Hospital, where the two who passed out regained consciousness. All were in stable condition last night. A police source said: 'Preliminary investigation showed that the boys had become ill after taking suspected ketamine. White powder was found in their nostrils.' The source added that they must have taken a substantial dose to fall so ill. 'Initial investigation showed that the trio bought the drug from their schoolmate and took it in the park.' Police said the schoolmate left after the transaction and was arrested on suspicion of trafficking in a dangerous drug at about 5pm. Detectives from the special duty squad of New Territories North region were trying to find the source of the drug. No charges had been laid last night. Headmaster Tam Man-kwan said two of the three boys were among six pupils at the school who were known to take drugs but said that with 1,079 students, he thought seven was 'not a very large figure'. The other four are two boys and two girls. He said the school would look into what it could do better to help students quit drugs and get on the right path. Social worker Ivy Jim Sek-chu of the Hong Kong Federation of Youth Groups, stationed in the school, said services including counselling were being offered to the six known drug users. The head of a church group working with young drug abusers said the case was quite serious. 'We should not tolerate one drug abuser at a school, let alone seven,' said Lau Wang-cheung, of the Evangelical Lutheran Church's Enlighten Centre. The Tin Tze Estate centre mainly serves young drug abusers in Tin Shui Wai. The three pupils were not clients there. 'We now have 65 active cases,' Mr Lau said. 'We also want to learn more about this case. Who is doing the case assessment? If the students are quitting the bad habit ... who is doing the supervision?' Representatives of the centre will visit the school next month to educate pupils on the dangers of drugs. The lawmaker for the social service sector, Peter Cheung Kwok-che, said social workers and teachers could not provide medical help for abusers to quit drugs. 'This has to rely on help from psychiatric doctors, but such services are seriously inadequate,' he said. According to Central Registry of Drug Abuse figures, the number of reported drug abusers aged under 21 rose from 2,278 to 3,430 between 2005 and last year. Cases of students taking drugs jumped from 583 to 913. In February, five girls aged 13 and 14 became ill in Sheung Shui Government Secondary School after taking suspected ketamine outside the school. Police arrested the girls, two other students and two youths in connection with the case. Last year 66 students were arrested for drug-related offences; three cases were in schools in the New Territories North. Law enforcers seized 22kg of ketamine in the first three months of the year, up from 20kg in the same period last year.