Facebook apologized to users that received notices asking if they were safe by mistake, following a suicide bomber that blew himself up in Lahore, Pakistan. The explosion killed dozens of people and Facebook enabled its Safety Check feature to make it easier for those in the area to let loved ones know they were OK.

But as well as asking people in Pakistan whether they were safe, Facebook also activated the feature and sent messages to people in other unaffected parts of the world. Facebook users in New York, Hong Kong, Cairo and numerous other places received messages asking "Have you been affected by the explosion?" with no reference made to Pakistan or Lahore. Facebook has issued an apology for any unnecessary worry this may have caused.

"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."

The flawed notices were the latest stumble in Facebook's evolving "Safety Check" practice.

In November, hours after blasts in Nigeria, Facebook activated Safety Check after criticism that it was being selective about deploying it.