Facebook confirmed in its latest earnings report an FTC investigation was underway, but didn’t go into much detail beyond it having to do with “the areas of social networking or social media services, digital advertising, and/or mobile or online applications.” The acquisition aspect is reportedly the focus of the investigation. Engadget has contacted Facebook for comment.

The company is said to have bought around 90 companies over the years. Along with the likes of Instagram and WhatsApp, they include Onavo, a data-saving service for phones that also tracked peoples’ app usage. Data from Onavo helped Facebook decide to buy WhatsApp and reportedly learn how Instagram Stories impacted Snapchat use. It shut down Onavo earlier this year.

The investigation follows another FTC probe of Facebook that led to a $5 billion fine against the company. That case was related to Facebook’s various privacy practices, particularly concerning the Cambridge Analytica scandal.

The Justice Department is also investigating if and how major tech companies have tried to stymie possible rivals. Regulators elsewhere are looking into competition concerns regarding Facebook too.