Facebook on Friday turned on its Safety Check feature after a large truck mowed through a crowd celebrating Bastille Day in Nice, France, killing at least 80 people.
According to CNET, it is the third time in nearly a month that the social networking giant has activated the tool.
The feature allows people to notify their friends if they are in the affected area and mark themselves as safe.
A click or tap on the "I'm Safe" button lets friends and loved ones know straight away. Users can also check to see whether their friends are safe too.
"Last month, we began testing features that allow people to both initiate and share Safety Check on Facebook," a Facebook spokesperson said in a statement.
"We hope the people in the area find the tool a helpful way to let their friends and family know they are OK," the spokesperson added.
The feature was activated in early June after the deadly attack on a Florida night club that claimed the lives of 49 people.
Less than two weeks later, Facebook activated Safety Check feature for users after a suicide attack that killed 45 people at Istanbul's Ataturk airport.