WhatsApp entirely back up and running now:  CEO Will Cathcart

In a series of tweets, Cathcart said,”We’re entirely back up and running now. We know that people were unable to use@WhatsApp to connect with their friends, family, businesses, community groups, and more today — a humbling reminder of how much people and organizations rely on our app every day.”

“We take our mission seriously, and I’m grateful to everyone who worked hard to bring our service back with the reliability you expect from@WhatsApp. We’ll learn and grow from this, and continue working to provide you with a simple, secure, and reliable private messaging app,” Cathcart further said.

Taking to Twitter early on Tuesday, WhatsApp said: “Apologies to everyone who hasn’t been able to use WhatsApp today. We’re starting to slowly and carefully get WhatsApp working again. Thank you so much for your patience. We will continue to keep you updated when we have more information to share.”

Monday’s outage has left several services under the Facebook corporate umbrella, including Instagram, WhatsApp and Messenger, inaccessible.

Facebook apologized but did not immediately explain what caused the failure, the largest ever tracked by web monitoring group Downdetector.

Several Facebook employees who declined to be named said that they believed that the outage was caused by an internal mistake in how internet traffic is routed to its systems, according to Reuters. The failures of internal communication tools and other resources that depend on that same network in order to work compounded the error, the employees said.

Security experts said an inadvertent mistake or sabotage by an insider were both plausible.

The error message on Facebook’s webpage suggested an error in the Domain Name System (DNS), which allows web addresses to take users to their destinations. A similar outage at cloud company Akamai Technologies Inc took down multiple websites in July.