Ho, Christine Fang Meng-sang and Margaret Ng Ngoi-yee were released in the evening, after they were arrested on Wednesday morning for conspirary to publish seditious content.

Ho walked out of Western Police Station at 5.30 pm on Thursday. She let the media take pictures outside the police station but left in a car without saying a word.

In less than an hour, Fang was released from Aberdeen Division police station. The former chief executive of the Hong Kong Council of Social Service pressed her hands together in a gesture of prayer and said it's not the time for her to talk.

Outside Central district police station, Ng stopped in front of reporters and said: "At this moment, the most important thing is that we continue to care for each other", adding that she "can't say too much for now".

Hundreds of national security police officers were deployed on Wednesday morning to raid the offices of online news outlet Stand News, arresting a total of seven people for conspiracy to publish seditious publications.

Four were former board members of the news outlet, including Ng, Ho, Fang and Chow Tat-chi. The four had each stepped down from their posts in June.

Acting editor-in-chief Lam Shiu-tung, 34, and former chief editor Chung Pui-kuen, 52, and Stand News' umbrella group Best Pencil (Hong Kong) Limited were charged with conspiracy to publish or reproduce seditious content. Their case was mentioned at the West Kowloon magistrates' courts on Thursday.

Acting chief magistrate Peter Law Tak-chuen rejected their bail pending their next court mention on February 25 next year.

Chung was brought by police to the court but Lam's lawyer said his client was diagnosed with a kidney condition last year and was sent to the Queen Elizabeth Hospital for treatment on Thursday.

He was discharged on afternoon and will appear in the court on Friday to hear his charges.

The prosecutor told the court Best Pencil's sole director Tony Tsoi Tung-ho is not in Hong Kong and a summon to require a company representative to attend the hearing was sent to two former employees of Stand News – closed down on Wednesday – including an administrative officer and the assistant editor-in-chief, but neither was willing to take the papers.

The prosecution in the afternoon sent another summon to Stand New's office at Kwun Tong but the company did not send any representatives to the hearing.

No plea was heard. The prosecutor said police has gathered sufficient evidence to charge the three defendants in the case, but officers have obtained a large amount of new evidence including six boxes of documents, more than 60 computers, 27 mobile devices and Lam's phone.

Police need more time to investigate the new evidence and decide whether more people will be charged.

Over 100 spectators attended the hearing, including a number of former Stand News reporters and representatives from the United States, United Kingdom, Netherlands and Germany consulates in Hong Kong.

Tsoi is wanted by the police, as well as former Stand News board member Joseph Lian Yizheng.

Lian, a former senior consultant at the Central Policy Unit, in October said he has migrated to Japan and is teaching at a university there while Tsoi has moved to Australia.

Chung’s wife Chan Pui-man, the former associate publisher of the now-defunct Apple Daily, has also been arrested for the same charge. She is remanded at Tai Lam Correctional Institution for another case involving Apple Daily.