Facebook said it blocked 115 accounts for suspected "coordinated inauthentic behavior" linked to foreign groups attempting to interfere in Tuesday’s U.S. midterm elections.

The company shut down 30 Facebook accounts and 85 Instagram accounts and is investigating them in more detail, it said in a blog post late Monday.

U.S. law enforcement officials on Sunday evening notified the social network about recently discovered online activity, "which they believe may be linked to foreign entities," Facebook’s head of cybersecurity policy, Nathaniel Gleicher, wrote in the post.

U.S. tech companies are stepping up security and efforts to fight disinformation campaigns to prevent online troublemakers from trying to divide voters and discredit democracy.

Gleicher said the company will provide an update once it learns more, "including whether these accounts are linked to the Russia-based Internet Research Agency or other foreign entities."

Almost all of the Facebook Pages associated with the blocked accounts appeared to be in French or Russian. The Instagram accounts were mostly in English and were focused either on celebrities or political debate.

At Facebook’s Menlo Park, California, headquarters this week, U.S. election activity will be monitored from a War Room with constant dashboards to keep tabs on what’s going viral. Facebook said it’s in contact with secretaries of state and state election bureaus to combat reports on any fake news on the site that could suppress voting.

Meanwhile, the company has expanded its fact-checking network to 14 other countries, where it works with local-language news organizations and fact-checkers. The program doesn’t extend to WhatsApp, the company’s popular messaging app that’s encrypted, where there’s no visibility into which stories are going viral. Viral content has also helped fuel lynchings in India and ethnic warfare in Myanmar, which Facebook has only started to address this year.

Last month, Facebook removed 82 pages, accounts and groups tied to Iran aimed at stirring up social strife in the U.S. and the U.K. It carried out an even broader sweep in August, removing 652 pages, groups and accounts linked to Russia and Iran. Twitter says it has identified more than 4,600 accounts and 10 million tweets, mostly affiliated with the Internet Research Agency, that it says were linked to foreign meddling in U.S. elections, including the presidential vote of 2016.