In a statement, the European Commission said, it is investigating how Facebook collects and monetizes its data. The development signals the opening of a second front, on top of an existing investigation, into Facebook’s marketplace.

As part of preliminary investigations into both Facebook and Google, the EU executive said, it had sent out questionnaires to both companies.

The move underscores growing concerns over the massive amount of data held by both tech giants and how they leverage this to block competitors and expand into new sectors.

“These investigations concern the way data is gathered, processed, used and monetized including for advertising purposes,” said the EU competition enforcer said, without providing details.

Facebook did not immediately respond to requests for comments.

The European Commission appears to be focusing on Facebook’s application programming interface (API) which allows app developers to access data or functionalities on its platform.

Data for marketing and advertising services is also in focus.

Regulators are also searching for answers in contracts which allow companies to access Facebook’s APIs as well as the impact on companies that are not allowed to use such data.