Twelve Hong Kong pro-democracy activists detained in Chinese waters while trying to flee to Taiwan are set to face prosecution after three months in detention on the mainland.

Police in the Yantian district of Shenzhen said on Friday they had completed investigations into the case of the 12, who were captured by Chinese coastguards on August 23 while fleeing on a speedboat.

A banner in the Chinese University of Hong Kong calling for support to save the 12 Hongkongers detained in China. Photo: Studio Incendo.

Most of those aboard were facing criminal charges in Hong Kong for offences linked to last year’s pro-democracy protests.

One of the fugitives was activist Andy Li, who was arrested on August 10 on suspicion of breaching the Beijing-imposed national security law by colluding with foreign forces.

The detainees have been accused of illegal border crossing or of organising the voyage.

In accordance with the law, the 12 “will be sent to Yantian District People’s Procuratorate for examination and prosecution,” Yantian police wrote in a posting on Weibo, China’s Twitter-like service.

It was unclear what charges they would face or what the maximum punishment may be.

Family members, who have been refused access, and activists have urged the Hong Kong government to press China to return the group to the city, which has a separate legal system to the mainland. But Hong Kong officials have said they would not interfere with law enforcement operations in another jurisdiction.

Last week, some relatives received letters from individuals in custody, stating that they were well-treated and urging their families not to worry. A concern group for the detainees raised doubts about the hand-written messages, saying mainland officials may have dictated the content.

A concern group for the 12 detained Hongkongers shares a photo of family members releasing balloon messages to their loved ones in mainland China.

Some ativists accused Hong Kong police of playing a part in the detention of the 12 activists. They said police had deployed air surveillance to track the boat before it entered Chinese waters .

Police chief Chris Tang later rebuffed the accusations as “malicious” and said the fugitives were to blame for deciding to jump bail.

Hong Kong police apprehended nine people last month for allegedly assisting the 12 fugitives by providing the boat, financial backing, accommodation before the trip and transport to the pier, and making arrangements for them in Taiwan.

Kelly Ho

Kelly Ho has an interest in local politics, education and sports. She formerly worked at South China Morning Post Young Post, where she specialised in reporting on issues related to Hong Kong youth. She has a bachelor's degree in Journalism from the University of Hong Kong, with a second major in Politics and Public Administration.