Facebook has deployed Safety Check, a feature designed to alert loved ones that you're ok in an emergency, after the Brussels terror attack.
Explosions at Zaventem airport and Maelbeek metro killed more than 30 people and seriously injured many more.
Some have criticised the tech company for not activating the feature earlier, however, while others have asked why it wasn't deployed in Turkey days ago when a bomb blast killed 36 in central Istanbul.
More than four million people used the feature in the aftermath of the terror attacks in Paris last year, but faced similar questions about how it chooses the emergency situations when it is activated.
Paris was the first time the feature had been used for an emergency situation that was not a natural disaster, explained Facebook vice president for growth Alex Schulz at the time, calling it a "work in progress".
The idea for Safety Check was spurred by the 2011 earthquake and Tsunami in Japan and was introduced in October 2014.
It works by sending you a notification if you're in the affected area. A simple response of "I'm safe" or "I'm not in the affected area is then posted automatically to your status. Anyone who has a friend who posts the status is also notified and the message can also be tagged to spread the message among loved ones.