Scores of police swooped on shopping malls and fast-food shops in Ma On Shan yesterday quizzing school students and confiscating their cigarettes in a move they said was designed to reduce juvenile crime. About 30 policemen stopped and searched students who were smoking in school uniform or simply talking with other youngsters. Students were sent on their way but publicly warned by the police. Those with cigarettes had them confiscated. Divisional Commander Tommy Chau Siu-keung said the operation could help prevent juvenile crime. 'Smoking is not a crime. But we should take preventive measures before they commit any offences. 'Similar operations will be stepped up especially with the start of a new school term,' he said. But a social worker warned the operation may have a negative effect and police had gone beyond their legitimate power. 'The children are not committing any crime. They should have their own human rights and privacy,' said James Leung Wing-yee, assistant director of the Boys' and Girls' Clubs Association of Hong Kong. 'Children should be respected, just like any citizen,' he said. But vice-principal So Man-kow of the Chiu Chau Association Secondary School in Ma On Shan welcomed the operation, saying it could help prevent the encroachment of triad members. 'If they [triad members] wait outside the school, we have no right to move them. The operation is a deterrent, preventing them approaching pupils,' he said. Juvenile crime in the New Territories South area rose by a third in the first half of this year.