SAN FRANCISCO – Acting on a tip from law enforcement, Facebook has removed more than 100 accounts – 30 on Facebook, 85 on Instagram – engaging in coordinated activity in French, English and Russian, raising the possibility that foreign actors are attempting to meddle on the eve of the U.S. midterm elections.

Facebook said it was alerted Sunday night to the suspicious activity that law enforcement believe may be linked to foreign entities and blocked the accounts in question. Almost all the Facebook pages appear to be in French or Russian while the Instagram accounts were mostly in English. Some were focused on celebrities, others on political debate, Facebook said.

"Typically, we would be further along with our analysis before announcing anything publicly. But given that we are only one day away from important elections in the U.S., we wanted to let people know about the action we've taken and the facts as we know them today," Nathaniel Gleicher, Facebook's head of cybersecurity policy, said in a blog post. "Once we know more – including whether these accounts are linked to the Russia-based Internet Research Agency or other foreign entities – we will update this post."

The investigation into the activity was announced late Monday. The company said it was too early in its investigation to determine who was behind the effort or how long the accounts had been operating. Facebook said it does not know how many people may have interacted with the Facebook and Instagram accounts.

A joint statement from the Department of Homeland Security, Department of Justice, the Office of the Director of National Intelligence and the FBI said law enforcement is working in "unprecedented ways" to combat foreign influence operations.

"Americans should be aware that foreign actors – and Russia in particular – continue to try to influence public sentiment and voter perceptions through actions intended to sow discord," the statement said. "They can do this by spreading false information about political processes and candidates, lying about their own interference activities, disseminating propaganda on social media, and through other tactics."

With Americans headed to the polls Tuesday, social media companies are on high alert for foreign interference. They are eager to show they will not permit a repeat of the 2016 presidential election during which Kremlin-linked Russian operatives at the Internet Research Agency used Facebook, Google's YouTube and Twitter to spread divisive messages on hot-button topics such as race and immigration to influence how people voted.

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After heavy criticism from lawmakers for failing to detect and purge election meddling in 2016, Facebook has made safeguarding elections around the world one of its top priorities. It has set up an elections "war room" on its campus in Menlo Park, California, where data scientists, engineers and other employees monitor foreign election manipulation, disinformation, voter suppression and other security challenges under a large American flag. It's also hired more people and strengthened automated systems to monitor what's posted on Facebook and it has introduced tighter controls on whocan buy political ads.

Last week, Facebook CEO Mark Zuckerberg told investors that his company was getting better at detecting foreign election interference but that "there are going to be things that our systems miss, no matter how well tuned we are."

In August, Facebook said it foiled political influence campaigns originating out of Iran and Russia that targeted U.S. users ahead of the midterm elections. The campaigns, which mimicked previous Kremlin-linked efforts to stir political discord around hot-button issues, also targeted users in the U.K., the Middle East and Latin America in a bid to sway world politics.

Two weeks ago, Facebook said it had uncovered another covert Iranian disinformation campaign which attempted to sow political discord in the U.S. on divisive issues ahead of the November midterm elections. The drumbeat of revelations underscore the difficult task of protecting elections from foreign interference on social media.

Iran and Russia have denied any involvement in Facebook disinformation campaigns.

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