Cases of Hong Kong people arrested on the mainland have slipped through the notification system because mainland officials are reluctant to inform the SAR, human rights groups say.
The notification system, which the SAR and Beijing launched on January 1, received its first three cases the same month and the number had soared to 70 by the end of last month.
But the figure does not reflect the actual situation because at least five cases have not been registered, according to checks by the Sunday Morning Post. The unreported cases involve the detention of SAR residents in Nanhai, Guangxi, Huizhou, Guizhou and Guangzhou.
Families of the five have sought help from the Society for Community Organisation and Isinolaw Research Centre, which offers free legal assistance to people facing a detention ordeal.
The Security Bureau has admitted it is following up on three cases brought to its notice by family members that did not pass through the notification system. It is not clear if these three cases involve those being handled by the two help groups.
All five cases being handled by the help groups fulfil the criteria for the notification mechanism.