Detention terms for Hongkongers nabbed in Shenzhen drug raids a week ago have suddenly been tripled under what a security official in the neighbouring city said was an agreement with Chief Executive Donald Tsang Yam-kuen. The increase, from five to 15 days, was imposed as part of co-operation efforts between the two cities to tackle cross-border drug abuse, according to the official at the Longgang detention centre, where the 119 people are being held. They were arrested early last Saturday at two entertainment venues in Shenzhen's Futian district, near the Lok Ma Chau border crossing. Friends and relatives of the detainees heard about their additional jail time when they went to the centre to collect them yesterday morning, when they were originally due for release. A detention centre official, who refused to give her name, said the authorities had decided to detain the Hong Kong people longer. 'We found their problems involving drug offences were much more serious than we thought,' she said. 'We have reached an agreement with your Chief Executive Tsang Yam-kuen as to the [detention release] postponement. 'They should take further anti-drug education. It's also a part of co-operation between Shenzhen and Hong Kong to tackle drug abuse.' The detention centre said on Monday that they would be released yesterday. Mr Tsang told lawmakers on Tuesday, three days after the arrests, that there was a pressing need to speed up anti-drug initiatives before the summer holidays to prevent youngsters from having their first drug experience this summer. The government said it would also share information with Shenzhen authorities to step up enforcement against cross-border drug users. Shenzhen acting Mayor Wang Rong promised in Hong Kong last month to step up co-operation on fighting worsening teen drug use and drug trafficking. A Security Bureau spokesman did not comment on the case yesterday but said Shenzhen and Hong Kong had agreed that teenagers detained in Shenzhen for drug abuse would be escorted back to Hong Kong at the end of their detention term. Veteran social services team leader Paul Lo Po-sing said detention terms for drug abusers in Shenzhen were usually about 15 days. Some detainees might even face month-long compulsory drug treatment if Shenzhen officials decided they were repeat offenders. Information about release dates from detention did not used to be as specific as now, Mr Lo said. A Hong Kong man turned away from the detention centre when he went to pick up two friends said he was very disappointed. 'My friends, both from Hong Kong, cannot get away until July 20,' he said. 'How can [Shenzhen authorities] chop and change like this? Under what rules? No one has explained it to us.' An elderly couple at the centre left quietly. 'Let him stay here longer. It might be a good lesson to him,' said the man, who refused to give his name or say whether they were waiting for a son or grandson. On July 1, Shenzhen's Public Security Bureau began a series of campaigns and raids against drug abuse, prostitution and gambling, especially at nightclubs, which could mean the arrests of more Hongkongers. The 24-hour opening of the border in 2003 boosted cross-border trips by young Hongkongers lured by lower prices of illegal drugs in Shenzhen. Shenzhen police have returned about 200 Hongkongers arrested over drugs since 2005.