Facebook's website went down temporarily on Thursday, showing an error screen when users attempted to log on to the social network.
"Sorry, something went wrong. We're working on getting this fixed as soon as we can," read the error message, which was displayed on a nearly blank screen.
The outage lasted about 30 minutes before the network was available again. It affected users in at least two continents - Europe and Asia - but may have been global.
"We are looking into this and I will get back shortly," a Facebook spokeswoman wrote in an email.
Twitter users tweeted complaints or joked about the outage with the hashtag "#facebookdown."
"Productivity worldwide raises 99999% since #facebookdown," quipped Twitter user Christian Seel.
The social network, which claims over 800 million daily active users, had a service problem last October, when network maintenance prevented users from posting status updates.
(Loek Essers in Amsterdam contributed to this report)