The global outage that plunged Facebook, its Instagram and WhatsApp platforms and many people who rely heavily on these services — including Facebook’s own workforce — into chaos Monday is gradually dissipating.

Facebook said late Monday that it's been working to restore access to its services and is “happy to report they are coming back online now." The company apologized and thanked its users for bearing with it. But fixing it wasn't as simple as flipping a proverbial switch. For some users, WhatsApp was working for a time, then not. For others, Instagram was working but not Facebook, and so on.

The company did not say what might be causing the outage, which began around 11:40 a.m. ET. Websites and apps often suffer outages of varying size and duration, but hourslong global disruptions are rare.

“This is epic,” said Doug Madory, director of internet analysis for Kentik Inc., a network monitoring and intelligence company. The last major internet outage, which knocked many of the world’s top websites offline in June, lasted less than an hour. The stricken content-delivery company in that case, Fastly, blamed it on a software bug triggered by a customer who changed a setting.

In Southwest Colorado, The Durango Herald’s and The Cortez Journal’s Facebook pages also were affected. The Herald and Journal Twitter accounts remained accessible.

In an unrelated complication, the Herald’s comment feature on its online stories was not functioning Monday.

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 (@Facebook) October 4, 2021

Facebook’s only public comment so far was a tweet in which it acknowledged that “some people are having trouble accessing (the) Facebook app” and that it was working on restoring access. Regarding the internal failures, Instagram head Adam Mosseri tweeted that it feels like a “snow day.”

But the impact was far worse for multitudes of Facebook’s nearly 3 billion users, showing just how much the world has come to rely on it and its properties – to run businesses, connect with communities of affinity, log on to multiple other websites and even to order food.

It also showed that, despite the presence of Twitter, Telegram, Signal, TikTok, Snapchat and a bevy of other platforms, nothing can truly replace the social network that has evolved in 17 years into all but critical infrastructure. Facebook’s request Monday that a revised antitrust complaint against it by the Federal Trade Commission be dismissed because it faces vigorous competition from other services seemed to ring a bit hollow.

The cause of the outage remains unclear. Madory said it appears Facebook withdrew “authoritative DNS routes” that let the rest of the internet communicate with its properties. Such routes are part of the internet’s Domain Name System, a central component of the internet that directs its traffic. Without Facebook broadcasting its routes on the public internet, apps and web addresses simple could not locate it.

So many people are reliant on Facebook, WhatsApp or Instagram as a primary mode of communication that losing access for so long can make them vulnerable to criminals taking advantage of the outage, said Rachel Tobac, a hacker and CEO of SocialProof Security.

“They don’t know how to contact the people in their lives without it,” she said. “They’re more susceptible to social engineering because they’re so desperate to communicate.” Tobac said during previous outages, some people have received emails promising to restore their social media account by clicking on a malicious link that can expose their personal data.

Jake Williams, chief technical officer of the cybersecurity firm BreachQuest, said that while foul play cannot be completely ruled out, chances were good that the outage is “an operational issue” caused by human error.

Madory said there was no sign that anyone but Facebook was responsible and discounted the possibility that another major internet player, such as a telecom company, might have inadvertently rewritten major routing tables that affect Facebook.

“No one else announced these routes,” Madory said.

Computer scientists speculated that a bug introduced by a configuration change in Facebook’s routing management system could be to blame. Colombia University computer scientist Steven Bellovin tweeted that he expected Facebook would first try an automated recovery in such a case. If that failed, it could be in for “a world of hurt” – because it would need to order manual changes at outside data centers, he said.

“What it boils down to: running a LARGE, even by Internet standards, distributed system is very hard, even for the very best,” Bellovin tweeted.

Facebook is going through a major crisis after the whistleblower who was the source of The Wall Street Journal’s series of stories exposing the company's awareness of internal research into the negative effects of its products and decisions went public on “60 Minutes" on Sunday.

Frances Haugen was identified in a “60 Minutes” interview Sunday as the woman who anonymously filed complaints with federal law enforcement that the company’s own research shows how it magnifies hate and misinformation, leads to increased polarization and that Instagram, specifically, can harm teenage girls' mental health.

The Wall Street Journal’s stories, called “The Facebook Files,” painted a picture of a company focused on growth and its own interests instead of the public good. Facebook has tried to play down the research. Nick Clegg, the company’s vice president of policy and public affairs, wrote to Facebook employees in a memo Friday that “social media has had a big impact on society in recent years, and Facebook is often a place where much of this debate plays out.”

Twitter, meanwhile, chimed in from the company’s main Twitter account, posting “hello literally everyone” as jokes and memes about the Facebook outage flooded the platform. Later, as an unverified screenshot suggesting that the facebook.com address was for sale circulated, Twitter CEO Jack Dorsey tweeted, “how much?”

The Journal of Cortez, Colorado, contributed to this article.