Facebook and its related sites, WhatsApp, Oculus and Instagram have been offline since around 5pm on Monday evening (UK time). Around six hours later, the social media network is back online again, after a global outage. The company hasn’t disclosed what the issue was yet, but Brian Krebs, a security reporter posted the following infomation on his website.

Brian said that the issue was probably due to some changes or issues on the routing behind Facebook, he noted that all of Facebook’s network was inaccessible via BGP (Border Gateway Protocol) and all routes from anywhere on the internet to Facebook was missing. Some reports online suggested that Facebook employees were having issues getting access to the offices and that some internal IT services were offline.