Facebook users as far away as New York and Virginia showed notifications they received on social media site Twitter.

"Unfortunately, many people not affected by the crisis received a notification asking if they were okay," Facebook said in a post on its site. "This kind of bug is counter to the product's intent... We apologize to anyone who mistakenly received the notification."

Some of the notices went out as text messages to mobile phones and asked, "Are you affected by the explosion?" without giving any indication of where, or how close, the recipients were to danger.