The Irish Data Protection Commission has opened a formal investigation into a data breach that affected nearly 50m Facebook accounts, which could result in a fine of up to $1.63bn. The breach, which was discovered by Facebook engineers on Tuesday 24 September, gave hackers the ability to take over users' accounts. It was patched on Thursday, the company said. "The investigation will examine Facebook's compliance with its obligation under the General Data Protection Regulation (GDPR) to implement appropriate technical and organisational measures to ensure the security and safeguarding of the personal data it processes," the commission said in a statement on Wednesday. The commission regulates Facebook's adherence to GDPR, a European law that strengthens the privacy protections of individuals and introduces harsh penalties for companies that fail to protect user data.