The information provided to Mueller included copies of the ads, information about the accounts buying them and their targeting criteria, the people said, according to the report. The information provided to Congress included copies of the ads and buyers' identities— information that the social network's own policy dictates would only be turned over via search warrant, those sources told the publication.
Former FBI Director Mueller was appointed by the Department of Justice to investigate Russian interference in the U.S. election.
Facebook didn't share that data with Congress partly amid concerns it might disrupt the Mueller probe and due to U.S. privacy laws, the people said, according to the report.
The report said a Facebook spokesperson said the company was continuing to investigate and was cooperating with authorities, and that a spokesperson for Mueller declined to comment.