Thirty-one school pupils, the youngest of them 13, have been arrested in raids on a triad gang which has been peddling drugs to teenagers in Tuen Mun, police say. The students were among 78 people held in the raids. All but 10 were boys or young men, and 67 were aged under 21. The suspected Sun Yee On triad members included a high number of teenagers because the gang targeted teenagers for recruitment, police said. Six of those held, including a 15-year-old boy, were suspected of selling drugs to teenagers in parks, entertainment venues and on public housing estates in the district. Police would not say whether any of the six were school pupils. An officer said: 'Intelligence also showed that some students were involved in illegal debt collection and were deployed to pour red paint on the doors of debtors' flats.' Senior Superintendent Daniel Leung Chin-wah, head of the New Territories North regional crime unit, said officers were still investigating whether the triad gang was involved in selling illegal drugs in schools. He said that in addition to drug trafficking and illegal debt collection, the suspects were believed to have been involved in assault, wounding, unlawful assembly, recruitment of people into a triad society and other triad-related offences. Leung said police had 'crippled' the triad gang with the arrest of its faction leader and core members in the operation. 'The operation also targeted the source of the drugs,' he said. 'We arrested five people who supplied illegal drugs to the teenage drug traffickers to sell to students in Tuen Mun.' Illegal drugs, including ketamine and Ice (methamphetamine), with a street value of about HK$20,000 were seized, and Leung said he believed the operation had hit the trade in illegal drugs in the district hard. Anti-triad officers had begun investigating the triad gang as it strengthened its influence in the district and targeted students and teenagers for recruitment about a year ago. Leung said police launched an operation, codenamed Knotmeter, and a police agent infiltrated the triad in November to collect evidence. The arrests were made on Tuesday when about 100 police, including officers from the police tactical unit, raided more than 70 entertainment venues and homes, mainly in Tuen Mun. Sixty-eight males and 10 females, aged between 13 and 40, were arrested. Thirty-one were students. Another officer said it was the first time an anti-triad crackdown had held more than 30 students in recent years. Sixty-nine were charged and would appear in Tuen Mun court today, while nine were released on bail pending further inquiries. Police said the alleged faction leader, 35, was arrested when officers raided his home in Tuen Mun on Tuesday morning. During the operation, officers seized water pipes, wooden rods, hoods and masks. Leung said the gang usually gathered in groups of 20 to 30 in parks, outside convenience stores and entertainment venues in Tuen Mun at night and was involved in bullying and assaults on passers-by. Tuen Mun district councillor Josephine Chan Shu-ying said stones had been hurled from the street, breaking a window in a flat, in an apparent revenge attack against the tenant who had complained about a group of youngsters gathering and shouting at Siu Hong Court after midnight several months ago.