Facebook said in a statement it is cooperating with the agency and declined further comment.
The FTC investigation, opened nearly a year ago, focuses on whether Facebook failed to honor previous privacy commitments when the political consulting firm Cambridge Analytica gained access to information about millions of users.
Facebook’s mishaps have since increased, with disclosure of a security breach affecting 50 million accounts and news that some of the world’s biggest technology companies were given more access to users’ data than had been disclosed.
The agency can’t impose fines on first-time offenders, only on companies that, like Facebook, have previously agreed to settle claims with the agency. The FTC can fine Facebook about $40,000 per violation and it is under pressure from lawmakers and privacy advocates to impose a stiff punishment against the company.