Facebook, already facing scrutiny over how it handles the private information of its users faced another cyber-attack on its computer network exposing the personal information of nearly 50 million users.

The breach which was discovered last week was the largest in the company’s 14-year history. The attackers exploited a feature in Facebook’s code to gain access to user accounts and potentially take control of them. Facebook said it had fixed the vulnerabilities and notified law enforcement officials. Company officials do not know the identity or the origin of the attackers, nor have they fully assessed the scope of the attack or if particular users were targeted. The investigation is still in its beginning stages. Security researchers suspect the breach affected even more people than Facebook estimated. Facebook would not say if the number of breached Facebook accounts is likely to grow. The unidentified attackers did gain access at least to basic demographic information such as gender, hometown, name or birthday that people include in their Facebook profile.