Facebook experienced its worst outage in 15 years on Wednesday night (14.03.19).
The social media network's main app, Facebook Messenger, Instagram and WhatsApp stopped working at around 4pm and the outage lasted for more than 14 hours.
Mark Zuckerberg's company were forced to address the blackout on rival site Twitter.
They wrote: "We're aware that some people are currently having trouble accessing the Facebook family of apps. We're working to resolve the issue as soon as possible."
They also denied reports that the outage was due to an attack from a Distributed Denial of Service (DDoS), which occurs when multiple systems flood the bandwidth or resources of a targeted system, usually one or more web servers.
They added: "We're focused on working to resolve the issue as soon as possible, but can confirm that the issue is not related to a DDoS attack."
Facebook are yet to reveal what caused the major problem.
However, there have been reports that it was knocked out by a Border Gateway Protocol (BGP) leak from a European internet service provider to a major transit ISP.
Roland Dobbins, the Principal Engineer of the network performance company Netscout, said: "While not malicious in nature, such events can prove disruptive on a widespread basis. It is very important that all network operators implement BGP peering best current practices."