Facebook users around the world were furious after being blocked from their accounts for reasons that have not yet been explained.

As they try to log in to their accounts, Facebook users receive a message saying: “Your Facebook account has been disabled because it did not follow our Community Standards. This decision can’t be reversed.”

Facebook’s parent company Meta confirmed the matter and said it had launched an investigation into the issue.

“We’re aware that some users are experiencing issues accessing their Facebook accounts and we are working to resolve them as quickly as possible,” tweeted Andy Stone of Meta.

While it is not yet known what the problem was, users are reported to have been locked out because they did not reply to a message that many thought was spam.

According to the report, some Facebook users received a mysterious spam-like email titled “Your account requires advanced security from Facebook Protect.” They were asked to turn on the Facebook Protect feature by a certain date.