Hong Kong police arrested 11 people on suspicion of aiding a group of pro-democracy activists, who are accused of trying to escape Hong Kong, local media reported on Thursday.
Those arrested range in age from 18 to 72, according to local broadcaster RTHK.
Among them was Daniel Wong, a lawyer who tried to help the 12 people that were detained in mainland China last August, after Chinese authorities intercepted their boat which was headed for Taiwan.
The group faced charges related to anti-government protests in the Chinese-ruled city in 2019.
Wong wrote on Facebook that police arrived at his apartment at 6 a.m.
Police later told Reuters they were still gathering information and could not make any immediate comment.
In late December, a Chinese court sentenced 10 of the 12 to between seven months and three years in prison for illegally crossing the border.
The detainees' plight has drawn international attention, with human rights groups raising concern as their families said they were denied access to independent lawyers.