Facebook is under scrutiny by European antitrust regulators who want information on whether the social network uses its size to squeeze smaller rivals.

The European Commission has sent questionnaires to Facebook’s customers and competitors about a range of practices, according to Bloomberg. Companies have been asked to respond by next week.

Officials are looking at Facebook’s sales platform and how it uses and shares data from apps.

The European Commission declined to comment.

Facebook as been under the focus of European regulators after revelations that it allowed the data of millions of users to be shared with political consultancy Cambridge Analytica.

The EU is also looking at how Amazon.com Inc. collects data from retailers through its platform, one of several cases examining whether internet firms play fair. Apple and Google have attracted antitrust complaints over how they treat competitors.

Facebook is also facing privacy probes over its policies and data breaches and was fined by the EU for failing to give correct information during the regulatory review of its WhatsApp takeover.