News was continuing to unfold quickly after a truck slammed into a Nice, France celebration, killing dozens.

As it has during past emergencies, Facebook is asking those nearby the chaos to check in as "safe." Those with loved ones in or around Nice can use the resource to see whether their friends or family are OK and have reported in.

The tool was introduced last year and widely used during the April Nepal earthquake, as well as the Paris attacks earlier this year.

In addition, those concerned about U.S. citizens overseas can call 1-888-407-4747 (from the US) or 202-501-4444 (from overseas) for assistance, the U.S. State Department has said during previous emergencies.