About 12 a.m. EST, Facebook users were able to regain access to their social media accounts after a 14-hour outage, according to CNN.
The outage was the longest in Facebook's 15 years, USA Today reports, and it spanned across the social network's family of sites, including Instagram and WhatsApp.
On March 13, Facebook users began reporting problems at 11:56 a.m., according to Buzzfeed News. Facebook officially filed a bug report at 3:32 p.m., citing "increased error rates."
"We are currently experiencing issues that may cause some [application programming interface] requests to take longer or fail unexpectedly. We are investigating the issue and working on a resolution," the report said, according to Buzzfeed News.
In a tweet, Facebook attributed the outage to a "service configuration change."
"Yesterday, as a result of a server configuration change, many people had trouble accessing our apps and services. We've now resolved the issues and our systems are recovering. We’re very sorry for the inconvenience and appreciate everyone’s patience."
Some users saw "required maintenance" messages during the outage. Others were simply unable to access Facebook, Instagram or WhatsApp for hours.
Quickly, rumors began to swirl that the outage was caused by a distributed denial-of-service attack, which occurs when hackers flood a company's network. Facebook denied the rumors in a tweet that "the issue is not related to a DDoS attack," according to CNN.
Facebook has not released additional information about the outage.
Network intelligence company ThousandEyes suggested the outage was internal.
"We saw '500 internal server errors' from Facebook. Given the sheer scale and continuous changes that these web scale providers are constantly making to their applications and infrastructure, sometimes things break as a result of these changes, even in the most capable hands," Alex Henthorn-Iwane, ThousandEyes' vice president of product marketing told Buzzfeed News.
Editor’s note: Becker’s updated this story at 1 pm CST to include the tweet from Facebook about the cause of the outage.