Facebook's facial recognition technology is being harnessed by the Missing Persons Advocacy Network (MPAN) in its searches for missing people.

The social network's auto-tagging function is being used to scan the backgrounds of user photos to look for the faces of missing persons.

This is taking place as part of a campaign titled Invisible Friends, which is encouraging social media users across the world to add the profiles of missing people as friends to provide the facial recognition technology with a greater number of images and videos to scan.

Loren O'Keeffe, founder and director of MPAN, explained: "Invisible Friends is an ingenious way to put artificial intelligence to work for a good cause, and carry out a task humans simply aren't capable of."

She added that billions of posts can be searched every week via this method, raising awareness for missing persons' families thanks to its potentially huge reach.