After acknowledging the problem Wednesday, Facebook remained mum on the issue for almost 24 hours before issuing an explanation and apology around 1630 GMT Thursday.
The spike in sign-ups, which was about five times higher than the norm, was likely a result of Wednesday's world-wide outage affecting Facebook, Instagram and WhatsApp, which are all owned by Facebook, Inc.e was not related to a DDoS attack, but have not yet specified what actually went wrong. "We're very sorry for the inconvenience and appreciate everyone's patience".
However, the latest Facebook service outage shows the issues that arise when attempting to consolidate a number of online services and apps together.
Facebook restored its services on Thursday after they went dark for many of its 2 billion users over a two-day period. Reuters was not immediately able to verify those claims and the company declined to comment beyond the statement on resumption of services.
"Have you tried turning it off and back on again?" replied one user after Facebook tweeted an update. Facebook's ad platform, Facebook Ad Manager, was also down. Amazon was reportedly allowed to see user contact information.
Media reports earlier said millions of users were affected, and thousands took to Twitter on Wednesday and Thursday to complain under the hashtag #facebookdown.
The news comes with regulators, investigators and elected officials in the United States and elsewhere in the world digging into the data sharing practices of Facebook.
Facebook has maintained that it shared limited amounts of user data with smartphone makers and other outside partners to enable its services to work well on devices or with applications.