Facebook has removed a network of suspected Russian-linked accounts and pages involved in organizing political events in the United States. The network is the most extensive effort to interfere in American politics that Facebook has found and made public ahead of November’s midterm elections.

The move comes as part of Facebook’s efforts to prevent a repeat of 2016, when accounts connected to a Kremlin-linked troll group posing as Americans ran rampant on its platform.

In briefings on Capitol Hill, Facebook has told lawmakers that it suspects a Russian group is behind more than 30 pages advocating US political stances, according to a congressional source briefed on the matter. One page promoted a “No Unite the Right 2” march — a counter demonstration to a planned “Unite the Right” event to coincide with the one-year anniversary of the march in Charlottesville in which a woman was killed. There was also an effort to amplify the “Abolish ICE” message pushed by liberals, the source said.

Publicly, Facebook is saying it does not know for sure who was behind the network, but is saying it has “found evidence of some connections between these accounts” and accounts that had been run by Russian trolls in the run-up to the 2016 presidential election. The company also said it had reported the network to law enforcement and to Congress.

Asked by CNN to respond to the reports, Russian Foreign Ministry spokesperson Maria Zakharova said, “I hope the materials will be officially presented to the Russian side.”

Facebook said the “Resisters” page, which organized the “No Unite the Right 2” event, recruited real activists who “unwittingly helped build interest in” the event” and posted information about transportation, materials, and locations so people could get to the protests.”

Facebook said it has contacted the real activists.

Nathaniel Gleicher, head of cybersecurity policy at Facebook, said in a post that the company was still investigating where the pages were run from but that, “Some of the activity is consistent with what we saw from the IRA before and after the 2016 elections.” (The IRA is the Internet Research Agency, a Kremlin-linked troll group that has been indicted by Special Counsel Robert Mueller’s office on charges related to an alleged conspiracy to defraud the United States.)

He cautioned, “But there are differences, too. For example, while IP addresses are easy to spoof, the IRA accounts we disabled last year sometimes used Russian IP addresses. We haven’t seen those here.”

“It’s clear that whoever set up these accounts went to much greater lengths to obscure their true identities than the Russian-based Internet Research Agency (IRA) has in the past. We believe this could be partly due to changes we’ve made over the last year to make this kind of abuse much harder. But security is not something that’s ever done,” the company said in a statement released Tuesday afternoon,” Facebook said in a statement Tuesday.

The removed pages had more than 290,000 followers, the company said. The most followed Facebook pages were “Aztlan Warriors,” “Black Elevation,” “Mindful Being,” and “Resisters.”

The company said the pages ran 150 ads for a total of approximately $11,000. The ads were paid for in US and Canadian dollars, the company added. In 2016, the Internet Research Agency had purchased ads targeting Americans using rubles.

Next week’s event was not the only event the pages created. The pages created about 30 events since May 2017 and “The largest had approximately 4,700 accounts interested in attending, and 1,400 users said that they would attend,” Facebook said.

Facebook has sought guidance from U.S. intelligence agencies in its attempt to prevent a repeat of 2016, when its platform was used to meddle in U.S. politics and society.