German Justice Minister Katarina Barley leaves after receiving her certificate of appointment from President Frank-Walter Steinmeier at Bellevue Palace in Berlin, Germany, March 14, 2018. REUTERS/Fabrizio Bensch/File Photo

BERLIN (Reuters) - German Justice Minister Katarina Barley said she planned a further meeting with Facebook to discuss the impact of its algorithms on the social network’s users, adding that recent disclosures of privacy violations were probably not isolated.

Facebook said on Wednesday that the personal information of up to 87 million users, mostly in the United States, may have been improperly shared with political consultancy Cambridge Analytica, more than previous estimates.

“I plan a further discussion with Facebook to discuss the question of algorithms [which] govern how people are categorized according to their usage of data,” Barley told reporters on Thursday.

Data privacy is a sensitive subject in Germany, where memories of the two 20th-century police states on its territory have spurred the government to take a leading role in pushing for tighter regulation of data-driven Internet giants.

A poll for ARD public television found that 61 percent of Germany’s internet users were concerned that their data had been misused, though only 12 percent said they had cut back on Facebook usage. A further 2 percent had stopped altogether.

The meeting with Barley will be the social network’s second such summons from the German government since the New York Times and London’s Observer newspaper broke news of the use of its data by Cambridge Analytica on March 16. Facebook shares have since lost 16 percent, wiping more than $80 billion from its market value.

“We should have no illusions: the Cambridge Analytica cases won’t be the only ones and Facebook is probably not the only Internet giant where similar doubtful cases occurred,” Barley said on Thursday. “It’s probably just the tip of the iceberg.”

Earlier, the British Information Commissioner’s Office (ICO) said Facebook was co-operating with its examination into how 30 organizations have used personal data, but that it was too early to say whether the social media giant had done enough.

The ICO said it was looking at how data was collected from a third party app on Facebook and shared with Cambridge Analytica, as well as a broader investigation into how social media platforms have been used in political campaigning.