Story highlights The Senate intelligence committee is probing Russia's use of social media

Facebook disclosed Wednesday it had sold ads to Russian troll farms

(CNN) Sen. Mark Warner said Facebook's disclosure that it sold political ads to a Russian troll farm was just the "tip of the iceberg" when it came to election interference on social media.

Facebook told congressional investigators Wednesday that it sold about $100,000 in political advertising -- roughly 3,000 ads -- to Russian troll farms from June 2015 to May 2017.

But Warner, the top Democrat on the Senate intelligence committee, said that he heard a different story from the social media giant during the 2016 election.

"It appeared to me that the very social media sites that we rely on for virtually everything -- our Facebooks, Googles and Twitters -- it was my belief the Russians were using those sites to intervene in our elections," Warner said Thursday, speaking at the Intelligence & National Security Summit in Washington. "And the first reaction from Facebook was: 'Well you're crazy, there's nothing going on' -- well, we find yesterday there actually was something going on."

Foreign influence on social media is just one area that Warner and the Senate intelligence committee are probing as part of their investigation into Russian election interference. Warner said that he wants the committee to hear more from Facebook, Twitter and other social media companies about Russian efforts.

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