The Federal Trade Commission is reportedly looking into filing a preliminary injunction against Facebook over antitrust concerns based on the interoperability of its apps. A potential injunction could focus on how Facebook interacts with Messenger, Instagram, and WhatsApp.

Reported by The Wall Street Journal, anonymous sources close to the matter have said FTC officials are looking into filing a preliminary injunction as soon as next month.

Facebook has been talking about creating stronger interoperability between its apps publicly for a year and plans have been progressing since. Official federal pushback on the company’s tighter integration of its apps has been expected by Facebook and WSJ’s sources say the company has been “worried” about it for months…

At the time of writing, Facebook’s stock has dropped almost 4% on the news.