Turkey’s Personal Data Protection Board (KVKK) Monday announced it had launched a probe into Facebook over the recent massive leak of personal data.

The probe comes after personal information, including phone numbers and full names of more than 530 million Facebook users were leaked online by hackers Saturday.

KVKK took the decision to initiate an ex officio investigation after discussing the issue at a meeting on the reports, Anadolu Agency (AA) reported.

The availability of the Facebook data set was first reported by Business Insider. According to that publication, it has information from 106 countries including phone numbers, Facebook IDs, full names, locations, birthdates and email addresses.

The information appears to be several years old, but it is another example of the vast amount of information collected by Facebook and other social media sites and throws doubt on how secure that information is.

Facebook has been grappling with data security issues for years. In 2018, the social media giant disabled a feature that allowed users to search for one another via phone number following revelations that the political firm Cambridge Analytica had accessed information on up to 87 million Facebook users without their knowledge or consent.

In December 2019, a Ukrainian security researcher reported finding a database with the names, phone numbers and unique user IDs of more than 267 million Facebook users – nearly all United States-based – on the open Internet. It is unclear if the current data dump is related to this database.

Security experts warned that the data could be fraudulently used by hackers.