Britain’s competition watchdog said on Friday it has opened an investigation into Facebook’s use of advertiser data as the EU announced a similar probe into the social media giant.

“We intend to thoroughly investigate Facebook’s use of data to assess whether its business practices are giving it an unfair advantage in the online dating and classified ad sectors,” Andrea Coscelli, head of the Competition and Markets Authority, said in a statement.

Coscelli said the CMA will be working closely with the European Commission as they each conduct their investigations. It is the third investigation into a suspected violation of competition law in digital markets, the CMA said, noting it is also probing Google’s “privacy sandbox” and Apple’s AppStore.

The CMA said it was looking into whether Facebook “might be abusing a dominant position in the social media or digital advertising markets through its collection and use of advertising data”.

Facebook collects data from its digital advertising services, which allow another business to advertise to its users, as well as from a “single sign-on” option that allows people to use their Facebook log-in to enter other websites and apps, the CMA said.

Facebook collects data from its digital advertising services, which allow another business to advertise to its users

The investigation will determine whether the US company unfairly used the data to benefit two services, Facebook Marketplace and Facebook Dating, which was launched in Europe last year.