The feature allows people in an affected area to demonstrate to their Facebook contacts that they are safe, following a major incident that caused loss of life. It was first deployed in April 2015, following a massive earthquake in Nepal.

The Paris attacks in November marked the first time it was used after a terrorist incident — a decision that attracted a great deal of criticism, due to the fact that dozens of people had been killed in attacks in Beirut, Lebanon, just the previous day.

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At the time, Facebook chief Mark Zuckerberg noted the criticism and said, while Safety Check had only been used after natural disasters in the past, it would be activated for more “human disasters” in future.

Facebook has made good on its word, turning on the feature after attacks that did not take place in western countries, such as those in Nigeria and Turkey.

At the time of writing, the death toll from bombings in the Brussels airport and metro stands at 26. The Belgian government has encouraged people in the capital to communicate via social media, as the phone networks are overloaded.

IMPORTANT: Brussels mobile networks are getting saturated. Please contact through data messages: Facebook, WhatsApp, Twitter. Avoid calls

— Alexander De Croo 🇧🇪🇪🇺 (@alexanderdecroo) March 22, 2016