Another source said she was arrested near her office.
Chow had earlier said she would go to Victoria Park on the evening of June 4 in a personal capacity to mourn the victims after police banned the rally on public health grounds, even though the city has not recorded a case of unexplained local transmission in more than a month.
The Alliance in Support of Patriotic Democratic Movements of China said it’s trying to verify the information that its vice-chairperson had been detained.
However, AFP quoted a police source as saying Chow had been arrested under section 17A of the Public Order Ordinance, which covers publicising unlawful assemblies.
Last year’s vigil was also banned on the grounds of the coronavirus. Tens of thousands defied the ban and rallied anyway in the park.
Police later arrested some two dozen democracy figures who attended that rally, some of whom have been given prison sentences, including other members of the Hong Kong Alliance. (Additional reporting by AFP)