BEIJING (Reuters) - Chinese police have detained two people who contributed to an online archive of censored articles about the coronavirus outbreak, a friend and a family member of one told Reuters on Monday.

The two - Chen Mei and Cai Wei - have been out of contact since April 19, when police detained them in Beijing, Chen Kun, Chen Mei’s brother, told Reuters.

Cai was held on charges of “picking quarrels and stirring up trouble”, on a notice from Chaoyang district police in Beijing, Chen Kun said, an accusation often used against political activists in China.

Chen Kun said he did not know what charges, if any, his brother was held on.

A third person, Cai’s girlfriend, surnamed Tang, was held on similar charges, Chen Kun said, although it was not immediately clear if she was directly involved in the archive project.

Chen’s family has not received any formal notice from the police. An officer said only that he was “cooperating with an investigation”, his brother said.

The Chaoyang district police referred a query to Beijing police headquarters, which did not immediately respond to a faxed request from Reuters for comment.

Chen Mei, 27, and Cai, who are old friends, were volunteers with a project called Terminus2049, an open-source archive that keeps records of censored articles from Chinese media on Github, a coding platform, Chen Kun said.

In recent months, the project has been active in making records of articles on the coronavirus outbreak, which originated in the central city of Wuhan late last year.

For a short time after the outbreak started, there was a window of relative openness for China’s online media to report aggressively on the virus.

But that ended in February as censors stepped in to shut WeChat groups, delete social media posts and tighten controls on the domestic media.

Many people who are active online, however, still found ways to share information.

The articles gathered on Terminus2049 touch on topics that can be seen as sensitive, including when human-to-human transmission of the new coronavirus was discovered.

The archive was among those that kept in circulation a profile report on a Wuhan doctor and whistleblower, Ai Fen, which went viral as people translated it in various forms including into Braille, Morse code and even Klingon in a defiance of the censors.

Ai was reprimanded in January for sharing information about the outbreak.

Chen worked at a non-profit organisation in Beijing and Cai worked at a tech company, said Lucy Qiu, a friend of the detained Chen.