• An internal Facebook investigation has found it is "likely" Russian operatives spent $100,000 on ads with "divisive messages"
  • About half of the funds potentially purchased ads intended to influence U.S. politics
  • Though most of the ads did not reference the U.S. presidential election or a specific candidate, they did mention "divisive social and political messages" about subjects including LGBT rights, race issues, immigration and gun control

Facebook has turned over all information about ads "likely" purchased by Russian operatives to special counsel Robert Mueller, according to a report.

A source familiar with the matter told Reuters on Wednesday that the social media giant had sent the former FBI director data including copies of the ads and the identity of the buyers. That report followed news that an internal Facebook investigation found it is agents of the Kremlin may have spent $100,000 on ads with "divisive messages" between June 2015 and May 2017.

A Facebook blog post published on Wednesday said the operation involved 3,000 separate ads over a two-year period and was likely to have been run out of Russia. In addition, Facebook found 470 affiliated fake accounts and pages.

Mueller is investigating Russian efforts to influence the 2016 election and whether the Trump campaign colluded with the Kremlin. The investigation has dogged and frustrated President Donald Trump, who has called it a "witch hunt" and a "hoax."

Robert Mueller

According to Facebook, about $50,000 of the funds — about 2,200 ads — were potentially related to affecting U.S. politics. The majority of the ads did not reference the presidential election, voting or a specific candidate. However, the ads focused on "divisive social and political messages" about hot-button topics including LGBT rights, race, immigration and gun rights. Facebook has shared its findings with U.S. authorities.

Facebook said in April that it found evidence some groups used its platform to sway the outcome of the election. It did not specify targets or who was behind the attack, but said its own findings did "not contradict" a U.S. Director of National Intelligence report in January about Russian efforts to influence the election.

The company has introduced technology improvements like machine learning to detect fake accounts, in addition to more tactics to stop the spread of misinformation and fake news. Some solutions also include decreasing the influence of "spammers" who spread false news links, lowering the number of articles with "clickbait" headlines that exaggerate information or do not present a full picture, and blocking pages from advertising if they share stories that have been flagged as being false.

—Reuters and CNBC's Jacob Pramuk contributed to this report.