At least eight members of the group have been taken away by police, while at least two are unreachable, according to activists and rights groups.
Police in Beijing's Xicheng district and in Zhuzhou did not respond to calls seeking information.
Tens of thousands of troops and tanks converged on Tiananmen Square to quash months of protests on the night of June 3-4, 1989. Several hundred people were killed - possibly several thousand - and more than 1600 people nationwide were subsequently jailed. The final prisoner, Miao Deshun, a factory worker from Beijing, was released in October, with serious mental and physical health problems.
Despite those tiny protests, few young Chinese people appear to have much knowledge or even interest in the events of June 4, 1989, according to Louisa Lim, author of The People's Republic of Amnesia: Tiananmen Revisited. That has followed nearly three decades of propaganda and censorship by the Communist Party aimed at suppressing and rewriting history.
"Those who do know about it tend to be largely supportive of the crackdown, because they believe this prevailing view that the party did what was necessary to ensure stability and that stability has paved the way for the country's three decades of economic development," she said.
"For young people, they see that their lives are better than their parents, and so they buy this narrative. It's a very black-and-white picture - chaos or stability - which precludes the possibility of any other outcome apart from repression, but these young people, whose ideas of what happened in 1989 are very sketchy and often completely incorrect, often have no reason to question it."
William Nee, China researcher for Amnesty International, called on the Beijing Government to come to grips with the crackdown and end the retaliation against anyone who dares mention the subject.
It is a very different story in Hong Kong, where tens of thousands gather every year to commemorate the crackdown. The self-governing territory had its own uprising for greater democracy in 2014, known as the Umbrella Movement, which failed to induce any concessions from the governments in Hong Kong or Beijing.