Facebook is back online after an outage left millions of people around the world Monday unable to use it, along with its Instagram and WhatsApp platforms, to connect with friends, family and others.
Facebook users said Monday evening that they have begun to regain partial access to the site, about six hours after it went down.
It later confirmed it had "reconnected to the global internet."
The outage began shortly before noon Eastern time. Thirty minutes later, Facebook tweeted:
"We're aware that some people are having trouble accessing our apps and products. We're working to get things back to normal as quickly as possible, and we apologize for any inconvenience."
Facebook officials have not said what caused the problem.
Mike Schroepfer, the company's chief technology officer, tweeted earlier Monday, "We are experiencing networking issues, and teams are working as fast as possible to debug and restore as fast as possible."
Reuters news agency reported that users could not access Facebook because they were not being directed to the correct place by the Domain Name System. It said Facebook controls that system, suggesting the problem was an internal one.
Facebook employees reported they lost access to some of their own tools Monday, making the company's response more difficult.
Instagram head Adam Mosseri tweeted that it "feels like a snow day."
Recently, The Wall Street Journal reported that internal Facebook documents showed the company knows about the negative effects of its products yet does little to counter potentially harmful consequences. CBS News' "60 Minutes" program broadcast an interview Sunday with a whistleblower, Frances Haugen, who aired her grievances about the social media giant.
Haugen is expected to testify before a Senate subcommittee on Tuesday.
Facebook said her allegations are misleading.
Facebook's vice president of policy and global affairs Nick Clegg pushed back against several of Haugen's assertions, including that its platforms are toxic for teens and suggestions it contributed to the January 6 riot.
"I think the assertion (that) January 6th can be explained because of social media, I just think that's ludicrous," Clegg told CNN.
Some information in this report comes from The Associated Press and Reuters.