Siu Yau-wai was in Shenzhen last night without Hong Kong or mainland documentation, according to his grandmother. The only identification document the 12-year-old holds is an expired two-way permit, which was used to bring him to Hong Kong nine years ago, Chow Siu-shuen, 67, said. While the motives behind his voluntary deportation from Hong Kong remained unclear, his chances of returning hinge solely on mainland authorities' willingness to grant him approval to return and reside in the city. In response to an inquiry from the Post about whether Yau-wai would be eligible to apply for Hong Kong residency, the Immigration Department reiterated yesterday that "for mainland residents who wish to come to Hong Kong for residence, they shall apply and seek approval from the relevant mainland authorities". Mainland authorities had yet to make public any view on the boy's situation. The Basic Law stipulates that people from other parts of China must apply for approval for entry to Hong Kong. Mainlanders wishing to enter must apply to the relevant authorities of their residential districts for approval, and must hold valid documents issued by the responsible authorities, a paper submitted to a Legislative Council security panel last year said. As a minor, Yau-wai may try to seek re-entry on the grounds of family reunion, since his grandmother is a permanent resident. Mainlanders who wish to settle in Hong Kong to reunite with family must apply for one-way permits from the Public Security Bureau at the place of their household registration, or hukou . The daily quota for the one-way permit scheme was set at 75 in 1982, increased to 105 in 1993, and to 150 in 1995. A mainland resident under 18 can apply for one of the permits if he or she has to depend on his or her parents who are settled here.