Facebook released the reaction feature to users worldwide in February after testing the emojis in select markets.
"We’ve been listening to people and know that there should be more ways to easily and quickly express how something you see in (the) news feed makes you feel," wrote Facebook product manager Sammi Krug in an announcement of the release in February. "That’s why today we are launching Reactions, an extension of the Like button, to give you more ways to share your reaction to a post in a quick and easy way."
Authorities in Belgium, however, say the relatively new feature can provide more information to the company than users meant to share.
"By limiting the number of icons to six, Facebook is counting on you to express your thoughts more easily so that the algorithms that run in the background are more effective," Belgium's federal police force wrote in a news release Wednesday. "The icons not only help to express your feelings, they also help Facebook assess the effectiveness of the ads on your profile."
Authorities said the reactions help Facebook determine the ideal space for companies to advertise on the site and also help zero in on what a user is most likely to be drawn toward.
It's not the first time officials in Belgium have come up against the social media giant. Late last year, Facebook was forced to stop using a cookie that tracked non-users who visited the site, according to BBC News.