Left Front activist Vasily Kuzmin has been taken in for questioning after investigators raided his apartment as part of the Bolotnaya case on Thursday.
Initially there was some confusion as to how many Left Front activists' homes had been searched by Investigative Committee agents.
"Searches in relation to Bolotnaya, Left Front, 3 people, Moscow. Our lawyer is on his way," RosUznik, a prisoners' rights group, wrote on Twitter on Thursday.
Vasily Kuzmin, Yelizaveta Kuchkina and Kristina Krasnova were named by Lenta.ru as the three people whose properties were searched in an operation that lasted for three hours.
RosUznik later confirmed through Twitter that only Vasily Kuzmin had been led away for questioning following the search of his flat, where the other activists were staying.
The Investigative Committee is yet to release an official statement regarding the search.
About 30 people are facing criminal charges over the Bolotnaya Ploshchad violence last May, when thousands took to the streets to protest against President Vladimir Putin's rule.
Two participants have already been sentenced to jail terms.