Facebook is denying that a service interruption this morning was caused by hackers.
Hacker group Lizard Squad had claimed they caused the fault, after also claiming an attack on Malaysia Airlines' website yesterday.
But in a statement, Facebook says the outage "was not the result of a third party attack" but instead occurred after they introduced a change that affected their configuration systems.
Facebook and Instagram are back up and running, and it is understood that no data was compromised.
The fault affected users world-wide and lasted for around 50 minutes.
Instagram - owned by Facebook - told users via its Twitter account earlier that it was aware of an outage and working on a fix.
AIM and Hipchat are also thought to have been affected.
Hacking group Lizard Squad - which recently claimed responsibility for a Christmas Day attack on PlayStation and Xbox Live services - said on Twitter that it was responsible for the problems.
Facebook, Instagram, Tinder, AIM, Hipchat #offline #LizardSquad
— Lizard Squad (@LizardMafia) January 27, 2015
A member of the group, who has previously spoken about the Christmas hack, posted a message "for all the mad people".
In the Twitter photo, he holds up a sheet of paper with "DOX ME" written on it - an apparent reference to "doxxing," a slang term for dumping personal data online.
The incident came a day after the group said it had hacked the Malaysia Airlines website - posting the message: "404 - Plane Not Found. Hacked by Cyber Caliphate".
Facebook had 1.25 billion monthly active users at the end of September.
The site is now working again but only after it became the subject of much controversy online.
It seems that Facebook has crashed. However, it's 6:30 a.m. here in Ireland, and quite late in the USA, if not the wee hours. Who's on FB?
— Tom Tooned (@toonedin) January 27, 2015
Facebook, Instagram, Tinder, AIM, and Hipchat all appear to be offline. We’ll keep you updated when we hear more.
— Engadget (@engadget) January 27, 2015
It's not just you! @Facebook and @Instagram are down right now http://t.co/r0C5QaKSsH pic.twitter.com/jhqgBse4MA
— The Next Web (@TheNextWeb) January 27, 2015
FACEBOOK AND INSTAGRAM ARE DOWN. TWITTER STAY WITH ME.
— Christine Riccio (@xtineMAY) January 27, 2015
That moment when you come on Twitter just to see if Facebook is down #facebookdown pic.twitter.com/0xD1nqe199
— EDM Maniac (@EDMManiac) January 27, 2015
Instagram confirmed that they were aware of an outage.
We're aware of an outage affecting Instagram and are working on a fix. Thank you for your patience.
— Instagram (@instagram) January 27, 2015
According to reports, the site was reported not working about 1:10am ET last night.
