FILE PHOTO: The Facebook application is seen on a phone screen August 3, 2017. REUTERS/Thomas White/File Photo

BRUSSELS (Reuters) - EU antitrust regulators are investigating how Facebook collects and monetizes its data, the European Commission said on Monday, opening a second front on top of an existing probe into the social media giant’s online marketplace.

The EU executive said it had sent out questionnaires as part of preliminary investigations into both Facebook and Google’s data.

The move underlines regulators’ concerns regarding the massive amount of data held by tech giants and how they may 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,” the EU competition enforcer said, without providing details.

Facebook did not immediately respond to a request for comment.

A questionnaire seen by Reuters showed the Commission zooming in on Facebook’s application programming interface (API) that allows app developers to access data or functionalities on its platform and its photo-sharing site Instagram and software components to interact.

Data for marketing and advertising services was also in focus.

Regulators wanted to know details of the contracts allowing companies access to Facebook’s APIs and the impact on companies if they were not allowed to use such data.

The questionnaire asked whether there were any restrictions or conditions on Facebook’s use of data provided by the companies in return for access to its APIs, and if Facebook curbs access and the reason for it.