Image: mkhmarketing Image: mkhmarketing

Users of Facebook were mostly unable to access its platforms for more than 14 hours on Wednesday, the company's biggest ever outage.

The disruption affected Facebook, Instagram, Messenger and WhatsApp, starting in the afternoon and only really recovering to full, normal service this morning. Facebook has yet to explain why it happened.

It last suffered such a sustained period of disruption in 2008, when it had just 150 million users.

Facebook took to Twitter to issue a statement, saying: "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."

Some rumours circling suggested it was the result of a Distributed Denial of Service (DDoS) attack, a type of cyber attack where huge amounts of traffic is directed to a platform to overload its databases. However, Facebook denied these rumours.

Although users were able to access the platforms, features were disabled. They could not post, refresh feeds or send messages.

The outage is likely to have come at a huge cost to Facebook as its revenues are based on users seeing advertising.

In a tweet, Steven Bartlett, founder of The Social Chain Group, highlighted the scale of the financial cost. He said: "Based on Facebook’s earnings, they generate $16.9 billion a quarter, which is $7.8 million an hour.

"So if their ads aren’t running, #FacebookDown & #InstagramDown could have already cost them up to $40,000,000."

The social media entrepreneur made the calculation just five hours into the disruption. Now, knowing that it lasted at least 14 hours, it could have cost Facebook nearly $110 million.