Facebook and Instagram are recovering from huge outages that began Wednesday.

Instagram tweeted "Anddddd... we're back." Facebook said "error rates have started to return to normal."

Facebook said the problems were caused by a "server configuration change."

Facebook and Instagram are getting back on their feet.

The two social networks, which together have billions of users, were down for hours Wednesday in one of the worst outages in Facebook's 15-year history. The BBC said it was the worst.

There were signs of life early Thursday morning, Eastern Time. Instagram tweeted "Anddddd... we're back," while reports of disruption on Facebook declined significantly.

In an update on its incident page on Thursday morning, Facebook said: "Error rates have started to return to normal however, you may still experience intermittent errors." This came nearly 24 hours after the problems started.

Read more: Facebook and Instagram go down for hours in major outage

Facebook's own metrics were supported by DownDetector, a website where people can report outages of popular internet services. Below is a graph from 4 a.m. ET — after reports of errors fell dramatically.

DownDetector

Facebook also disclosed the reason for the collapse on Thursday, telling Business Insider: "We made a server configuration change that triggered a cascading series of issues. As a result, many people had difficulty accessing our apps and service."

A spokesperson added: "We have resolved the issues, and our systems have been recovering over the last few hours. We are very sorry for the inconvenience and we appreciate everyone's patience."