(CNN)Facebook originally proposed trekking to the Hill in the middle of the August recess, a traditionally quiet time when much of Washington is on vacation, but that idea was immediately met with pushback from Hill investigators who argued nobody would be in town, sources said Friday.
Facebook briefings first proposed for dead of August
Facebook officials were overruled by Hill investigators, who said the tech giant would have to reveal its findings on the Russian purchase of ads during the 2016 election when Congress returned in September, one source familiar with the discussions said.
A second source familiar with the matter said that mid-August was floated not to downplay the findings, but because that's when Facebook said it was first prepared to talk with Congress. When Facebook officials finally did show up to the Hill Wednesday, they revealed the bombshell that a Russian "troll farm" linked to the Kremlin had purchased $100,000 worth of ads -- some of which appear designed to plug Facebook users into streams of fake news and Russian propaganda.
For Facebook, and Hill investigators, it was a stunning new revelation just months after the company said it had discovered no evidence of Russian operatives buying ads on its platform.
But US intelligence officials have been tracking Russia's efforts to push propaganda and fake news over social media for years. And the FBI, specifically, was aware of the Russian ad buys well before Facebook revealed them to congressional investigators, two US officials said.
The officials said that federal investigators have not shared their findings with Facebook because of the classified manner in which they were obtained.
Facebook's public statement issued Wednesday, that it had discovered the ads and shut down hundreds of fake accounts related to the Russian "troll farm" -- quickly put the tech giant at the center of the Russia investigations in a way that it had largely avoided since the election last year.
Hill investigators clearly want to bring Facebook officials back to the Hill to explain more, but have not proposed any specific dates or options yet, said one source familiar with the discussions.
Sen. Mark Warner, the top Democrat on the Senate intelligence committee, said Thursday he also wants to hear from Twitter officials about Russia's use of "botnets" -- thousands of fake Twitter accounts -- to push propaganda during the campaign. A project started by counterterrorism expert Clint Watts and the German Marshall Fund, dubbed "Hamilton 68," has also shown that many of the fake accounts are still active, pushing coordinated messages.
Warner in particular has been ardent trying to get answers out of Facebook -- traveling to the company's California headquarters this past May and negotiating with them throughout the summer. Warner said Friday he felt vindicated by Facebook's announcement this week, but he still wants more answers.
"I do recall when I started raising these issues as early as last winter, they were pretty dismissive," Warner said. "So they -- they, and Twitter and others -- we need a lot more answers."
Rep. Joaquin Castro, a Democrat on the House intelligence committee who has been focusing on Russia's social media efforts, said: "It would be irresponsible not to bring in Facebook, Twitter and others."