"We're very sorry for the inconvenience and appreciate everyone's patience", Facebook said.
Facebook first acknowledged the problems in a tweet Wednesday at 1:49 p.m. ET, then said in a follow-up message that it was able to confirm the outages were not caused by distributed denial-of-service attack, in which networks are overloaded with bogus traffic created to disrupt service. Facebook said the issue had been resolved and that it's systems were recovering. The company did not immediately respond to a request for comment.
Facebook and Instagram has been coming back online for most users on March 14, but it appears it's not completely out of the woods yet. DownDetector, a website that allows users to report when a service isn't working, first started receiving a flood or reports starting around 12:01PM ET.
Facebook estimates that 2.7 billion people use its apps, with more than 2 billion users posting and messaging on its services every day. Facebook product director Rob Leathern said on Twitter that people were also unable to access the social network's ad interfaces, which may exacerbate any lost revenue from the outage.
Facebook's stock fell almost 3% in early morning trading on Thursday as Wall Street reacted to the outage.