Sources told RTHK that national security police on Tuesday took in for questioning the parents of national security suspect Anna Kwok.
Kwok is one of eight people living overseas who are wanted by police for alleged national security offences, with rewards of HK$1 million offered for information leading to their capture.
Officers were seeking information on whether Kwok's parents had any contact or financial dealings with their daughter, RTHK understands.
Relatives of several other suspects are also believed to have been questioned by national security police in recent weeks.