Facebook administrators have deleted up to 80 percent of the groups associated with the “Internet Research Agency,” an organization known as Russia’s biggest “troll factory.” A source close to the agency told the newsletter The Bell that administrators have shut down 25 Facebook communities with a total subscriber count of more than 3 million accounts, and 32 groups on Instagram with 2 million subscribers. The same source says Twitter also blocked 50 of the Internet Research Agency’s accounts with a combined follower count of 600,000 users.

According to The Bell, the groups and accounts in question were created ahead of the 2016 U.S. presidential election. The source says the Internet Research Agency still maintains a sizable presence on Facebook, Instagram, and Twitter, “in case the networks are needed again.”

The Bell says the likelihood that the remaining groups will be blocked is low: most of the users in these communities are real people, not bots, and the only way Facebook could determine that they’re owned by Russia’s “troll factory” would be “through advertising campaigns.”

The Internet Research Agency employs paid writers to spread online comments and posts intended to “influence” Internet users. The agency has been tied to Evgeny Prigozhin, a billionaire restaurateur known as Vladimir Putin’s “favorite chef.”

According to an investigation by RBC, the same “troll factory” is tied to a network of obscure and unreliable online publications with a collective monthly audience of 35 million readers.

On September 6, 2017, Facebook revealed that it had uncovered 470 “inauthentic accounts and pages” that distributed political advertising apparently managed from Russia. The ads addressed political controversial topics in the United States, including LGBT rights, race relations, and gun ownership. According to The New York Times, Facebook suspects that many of these accounts were controlled by the Internet Research Agency.