Facebook indicated that nearly 500 fake accounts purchased roughly 3,000 political ads between June 2015 and May 2017, according to Alex Stamos, Facebook’s chief security officer.
Facebook also found an additional 2,200 political ads tied to Russia in a broader search of company records. The ads, purchase from the company for roughly $50,000, did not violate any company policies or laws, Facebook said in a statement.
The company briefed House and Senate Intelligence Committee staff on its internal findings, according to committee aides.
"I think there’s a lot more to be discovered, and a lot more transparency that’s needed from Facebook, Twitter and other firms," he said. "My hope is at some point we even have Facebook and Twitter and some of the other social media firms here for a public hearing."
He also revealed that Twitter will give his staff a similar briefing "soon."
In their meetings with congressional staff, Facebook officials gave specific examples of geographically targeted ads, Warner said. Approximately one-in-four ads identified by Facebook were geographically targeted. (A Facebook official declined to share examples of any ads with ABC News.)
They also told investigators that the fake accounts were created by the Internet Research Agency, a so-called "troll farm" in St. Petersburg with ties to the Russian government.
Warner said he believes the universe of ads and fake accounts is much larger than what Facebook disclosed today.
"These enterprises have huge amounts of information. Their ability is to mine and utilize that data. I’d like to get a more comprehensive look that what we got today. I think today was a good first step but I think there’s more to come," he said.
He also said his committee is no closer to answering the "$64 million dollar question": if the Russians behind the ads received any guidance from Americans involved in the election.
"I don't have the answer to that yet," he said. "Before this investigation is over we have to answer those questions."