Among the Facebook and Instagram accounts that were linked to Russian trolls ahead of the U.S. midterm elections this month, one on Instagram had more than 600,000 U.S. followers, Facebook said in a blog post on Tuesday.

A Russian troll farm was tied to more than 100 Facebook and Instagram accounts before they were blocked on the eve of the elections, Facebook said.

Based on a tip from the FBI on Nov. 4, the company identified and removed a total of 99 Instagram accounts, 36 Facebook accounts and 6 Facebook pages. About $4,500 in ad spending came from those pages, though none of the ads ran in the U.S., the company said.

The accounts may be connected to the Internet Research Agency, Facebook said. That's the same group responsible for Russian interference in the 2016 U.S. presidential election, according to a February indictment by Special Counsel Robert Mueller.