Mark Zuckerberg's Facebook being scrutinised in Ireland

Personal information on 533 million Facebook users reemerged on a hacker website for free on Saturday.

FILE- In this May 1, 2018, file photo, Facebook CEO Mark Zuckerberg delivers the keynote speech at F8, Facebook's developer conference in San Jose, Calif. Details from more than 500 million Facebook users have been found available on a website for hackers. 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 the limits to how secure that information is. (AP Photo/Marcio Jose Sanchez, File) (AP)

Facebook Inc.'s top privacy regulator in the European Union said it's looking into a leak over the weekend of the personal data of more than half a billion users of the social media service.

The Irish Data Protection Commission is trying to “establish the full facts” since the weekend and so far “received no proactive communication from Facebook,” the regulator said in a statement on its website on Tuesday. It said the tech company assured it that “it is giving highest priority to providing firm answers” to the authority.

Personal information on 533 million Facebook users reemerged on a hacker website for free on Saturday. The information included phone numbers and email address of users, the regulator said Tuesday. Facebook has said the data is old and was already reported on in 2019.

The data largely seems to stem from a “large-scale scraping” of Facebook's website before the EU's strict data protection rules took effect, the Irish authority said.

“A significant number of the users are EU users,” it said. “Much of the data appears to been data scraped some time ago from Facebook public profiles.”