Facebook apologized for an hours-long outage Monday.
"We apologize to all those affected, and we’re working to understand more about what happened today so we can continue to make our infrastructure more resilient," Facebook’s VP of Infrastructure, Santosh Janardhan.
Facebook, Instagram and WhatsApp were essentially inoperable Monday afternoon.
The programs began coming back online Monday evening.
In a blog post, Janardhan attempted to explain the cause of the outage.
"Our engineering teams have learned that configuration changes on the backbone routers that coordinate network traffic between our data centers caused issues that interrupted this communication," he said. "This disruption to network traffic had a cascading effect on the way our data centers communicate, bringing our services to a halt."
While Facebook, Instagram and WhatsApp are back online, users have said all their functions aren't working.
Janardhan addressed those concerns Monday night.
"Our services are now back online and we’re actively working to fully return them to regular operations," he said.
Janardhan also stated that the outage was caused by a "'faulty configuration change," and there is no evidence that data was compromised.