The tech giant could be hit by an antitrust lawsuit as soon as the end of this year, the Wall Street Journal reports, as the regulator examines whether Facebook has used its market dominance to quash competition.

The FTC has been investigating concerns about Facebook’s dominance for “more than a year,” and staffers have already taken testimony from Facebook CEO Mark Zuckerberg. It has not yet made a decision on whether or not it will sue Facebook, and details of how the FTC would go about it were also not available.

Any lawsuit against Facebook would require a majority vote from the FTC’s five-person commission, which is currently comprised of two Democrats and three Republicans.

It’s not Facebook’s first run-in with the FTC. The Menlo Park, Calif.-based company was hit with a record-shattering $5 billion fine last year following the FTC’s probe into Facebook’s 2014 promise to stop allowing third-party developers to access data from the “friends” of app users.

Instead, FTC says, Facebook “grandfathered” developers already on the platform, including British consulting firm Cambridge Analytica, known for using a personality test to better target voters with ads ahead of the 2016 presidential election.

A representative for Facebook did not immediately respond to a request for comment.