Germany’s Cartel Office on March 26 announced it is investigating Facebook’s use of data it culls from partner websites. Meanwhile, the justice minister has called executives from the social media network to discuss privacy concerns.

In an interview with Germany’s Tagesspiegel newspaper, the president of the Cartel Office, Andreas Mundt, said users were largely unaware how much information flowed to the social network when they visited third-party websites with Facebook integration.

He said his office was working on the basis of possible abuses stemming from “the collection and assessment of data from third-party sources outside Facebook”.

As reported by the Reuters news agency, Facebook is at the centre of a storm over allegations that data from millions of its users was improperly used by consultants Cambridge Analytica to target US and British voters in close-run elections.

“Interfaces to other web pages allow data to flow to Facebook,” Mundt said. “That happens even if you don’t click the ‘Like’ button, but load a website with one embedded,” he added, saying users were often unaware of this.

According to Reuters, the cartel office is already examining whether the network is abusing what Mundt called its “market-controlling position”.