Mainlanders jailed in Hong Kong could be sent back across the border to serve their time in a move that would ease congestion in the city's crowded prisons. Mainland officials have agreed to discuss the idea, Secretary for Security Ambrose Lee Siu-kwong said in Beijing yesterday. Speaking after a meeting with Zhang Xiaoming , deputy director of the Hong Kong and Macau Affairs Office, Mr Lee said there were about 4,000 mainlanders serving sentences in jails in Hong Kong. They accounted for 30 per cent of the total prison population. Mr Lee said Hong Kong had reached agreements on transferring convicts to their place of origin with many countries and that it had completed similar talks with Macau. 'We hope to discuss the matter with mainland authorities. Mr Zhang's responses were very positive and it was agreed that both sides could explore the issue again in the near future,' Mr Lee said.