Facebook’s ongoing fight against fake news is one of the biggest controversies the site has faced in years. Some more fuel was added to the fire this week when a fake news report of a bomb blast in Bankok, Thailand, caused the site’s Safety Check feature to trigger.

The false alarm lasted for about an hour, and prompted users within the city to mark themselves as safe. Facebook listed “Media Sources” as confirmation of the blast, but a Channel NewsAsia reporter shared a screenshot of the news stories that accompanied the alert showing the top result from an untrustworthy news aggregator. The fake news-scraping story included video from a real 2015 bombing.

Facebook announced last fall that Safety Check would be triggered by an algorithm that looked at trending news and posts from users in the area. At the time, Facebook said it used third-party software to fact-check news before using it as justification to trigger a Safety Check. However, that was obviously not the case here, and now questions need to be raised about how the tool determines what’s true. Many critics of Facebook have expressed concern with the long-term psychological effects of fake news, but as this case illustrates, it can have more immediate and dangerous consequences, too.