Facebook and Facebook-owned apps Instagram and WhatsApp were up and running again late Monday after being hit by an outage that affected users around the world.
Facebook apologized for the problem, saying the lack of access was caused by "configuration changes on backbone routers that co-ordinate network traffic between data centres."
The social media giant said the disruption to network traffic "had a cascading effect on the way our data centres communicate, bringing our services to a halt." It said there is no evidence that user data was compromised.
Users reported being unable to log into any of the services a little before noon eastern time on Monday. Facebook posted a message to Twitter around 6:30 p.m. saying they were "happy to report they are coming back online now."
It was the largest such outage ever tracked by the web monitoring group Downdetector, which collates complaints about web outages.
Downdetector said there were more than 30,000 Canadians complaining about an outage. Instagram logged 21,000 reports of outages, while there were at least 14,000 reports about WhatsApp in Canada alone.
Reports of similar outages emerged throughout the U.S., Europe, Africa and Asia.
About 30 minutes after it began, Facebook acknowledged the outage in a tweet, saying that around the world some "people are having trouble accessing Facebook app. We're working to get things back to normal as quickly as possible, and we apologize for any inconvenience."
Doug Madory, director of internet analysis for network technology firm Kentik Inc., said it appears to be related to the Domain Name System (DNS), which routes internet traffic to where it is supposed to go.
A DNS server is how an internet user typing in a text-based website address such as Facebook.com gets sent to the correct numerical IP address.
Facebook would be in charge of its own DNS service, but Madory said the routes being made available to its sites for its networking partners were withdrawn, resulting in a "near complete global outage" of all Facebook properties.
WATCH | Facebook, Instagram, WhatsApp back online after outage:
Cybersecurity analyst Ritesh Kotak told CBC News early in the outage that it was likely the result of an internal error and not a hack on the company by outside forces.
A similar DNS outage was to blame when problems at networking company Akamai wiped out internet traffic to thousands of websites around the world this summer.
Matthew Prince, CEO of the internet infrastructure provider Cloudflare, tweeted that "nothing we're seeing related to the Facebook services outage suggests it was an attack."
Prince said the most likely explanation was that Facebook mistakenly knocked itself off the internet during maintenance.
The outage came as the social media giant was once again coming under intense scrutiny for the way it does business.
Last week, it halted plans to develop a version of its photo and video sharing app Instagram designed specifically for children.
Then over the weekend, a former manager blew the whistle on the company's involvement in feeding the Jan. 6 insurrection at the U.S. Capitol.
The whistleblower, Frances Haugen, will tell her story to U.S. lawmakers on Tuesday.