Facebook said Tuesday that it had discovered a sophisticated coordinated disinformation operation on its platform involving 32 false pages and profiles engaging in divisive messaging ahead of the U.S. midterm elections.

The social media company said that it couldn’t tie the activity to Russia, which interfered on its platform around the 2016 presidential election. But Facebook said the profiles shared a pattern of behavior with the previous Russian disinformation campaign, which was led by a group called the Internet Research Agency.

Facebook briefed congressional aides this week. A congressional aide said there’s no evidence that political candidates were targeted in the new disinformation effort, but that pages and accounts sought to spread politically divisive content around social issues.

“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,” Facebook said in a post. “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. We face determined, well-funded adversaries who will never give up and are constantly changing tactics. It’s an arms race and we need to constantly improve too.”

In particular, the pages promoted an event pegged as a counter-rally to a far-right march scheduled for next weekend in Washington, D.C. Facebook said that the urgency of the upcoming rally prompted them to publicize the information, even though it is in the early stages of an investigation.

The company, which identified the pages two weeks ago and has since removed them, said in June that it had found no such activity.

The 32 pages found had up to 18,000 followers. There was no specific evidence that political candidates were targeted, but one account followed an IRA-associated account for a brief period of time.

“Today’s disclosure is further evidence that the Kremlin continues to exploit platforms like Facebook to sow division and spread disinformation, and I am glad that Facebook is taking some steps to pinpoint and address this activity,” said Sen. Mark Warner, D-Va. “I also expect Facebook, along with other platform companies, will continue to identify Russian troll activity and to work with Congress on updating our laws to better protect our democracy in the future.”

In the runup to 2016 election, Russian operatives spread false messages using hundreds of accounts. These messages went viral, reaching over 100 million Americans.