Schoolgirls as young as 16 are being lured to work as prostitutes after being offered jobs as waitresses at Mongkok karaoke clubs. Police say the teenagers are persuaded to work as hostesses - or so-called PR girls, who sing and drink with clients - after being told they could take home more than $1,000 a day. However, they earn as little as $50 per client and may have to work from 2pm to 4am. The warning follows the arrest of 11 students, aged 16 to 17, in one week during undercover operations at three nightclubs. Police said some of the girls were recruited through newspaper ads, while others were introduced by friends. Officers said the schoolgirls were encouraged to earn extra money working as hostesses after being offered summer jobs as waitresses with monthly salaries of between $6,000 and $7,000. 'PR girls are paid $100 an hour to sing and drink with clients. Of course, they allow their clients to touch their bodies,' a police source said. 'They can earn extra money by providing various sex services inside the [private] singing rooms.' The girls receive only half the fee paid by clients for sex services, which can cost as little as $100. On Thursday night, undercover police visited a karaoke club in Tung Choi Street, Mongkok, where they arrested 30 people including five students aged 16 or 17. Officers arrested more than 40 people, including six students aged 17, during similar operations last week at two other Mongkok karaoke clubs. 'We believe most nightclubs have triad connections. But investigations revealed that none of the arrested girls were forced to work as PR girls or offer sex services to their clients,' another source said. The raids were carried out as part of an operation against youth-related crime in Mongkok during the summer school break. Senior Inspector Lee Kwok-chiu, the district's assistant operations officer, said police had applied for care and protection orders for the arrested girls. He said officers would continue to collect information and crack down on vice-related crimes in the district. 'Students must be cautioned while looking for summer jobs. They should be alerted about the possibility of falling into traps and being controlled by criminals to make money,' Senior Inspector Lee said. 'Parents should also be alerted if they notice their children going out frequently at night or suddenly having a lot of money to buy expensive goods.'