Facebook users looking for more context on why the Sept. 11 terrorist attack anniversary was trending on the platform on Friday were, for a time, directed to a tabloid article claiming that “experts” had footage that “proves bombs were planted in Twin Towers.”

The Daily Star piece promoted by Facebook repeats a lot of common claims from 9/11 “trutherism,” a conspiracy theory based on an idea (unsupported by any actual evidence) that the World Trade Center must have collapsed in 2001 because of a “controlled demolition” and not from the damage caused by the airliner crashes.

Here’s what The Intersect saw when it hovered over the “September 11th” trending topic on Friday morning:

If you clicked on the actual trending topic, Facebook directed you to the following page:

Shortly after The Intersect reached out to Facebook for a comment on the matter, the article disappeared from Facebook’s page for the topic. The lead article switched to a local news piece about a photograph showing beams of light bouncing off One World Trade Center.

“We’re aware a hoax article showed up there,” a Facebook spokeswoman said in a statement on Friday, “and as a temporary step to resolving this we’ve removed the topic.”

The misstep comes weeks after the company removed the human editors who used to describe and curate the site’s trending topics, leaving the task of providing context for those topics to an algorithmically selected article from another site. As this most recent example illustrates, the algorithms haven’t always been up to the task.

Just days after Facebook announced the switch, Megyn Kelly trended on the platform because of a factually incorrect story that called the Fox News anchor a “traitor” and claimed that Fox had “Kick[ed] her out for backing Hillary.” Facebook later apologized for the mistake.

The task of determining which topics make it to Facebook’s trending lists — which are customized for each user based on a number of factors — have always been largely left up to algorithms. But human editors with a background in journalism have, until recently, been a part of the process as well, guiding and tweaking what the algorithms surface — and checking for mistakes. How, exactly, that happened, was largely a secret until Gizmodo published a series of reports last spring, detailing what it was like to work for Facebook as a journalist.

At least one former employee of the company told Gizmodo that the process was biased against politically conservative news topics. And although both Facebook and other former employees of the trending team have since said that accusation wasn’t quite right, it set off a huge controversy over possible political “bias” on the platform.

That larger discussion was important for the same reasons raised by Facebook’s mistakes today. Although Mark Zuckerberg has said that Facebook is “not a media company,” in reality the platform plays an enormous role in determining the news that people see across the world.

The recent changes to Facebook’s trending process were widely seen as an attempt to address the perceived “bias” in the system. The company said in August that it had accelerated the process of diminishing the algorithm’s editorial oversight — something it always intended to do — “given the feedback we got from the Facebook community earlier this year.”

Facebook’s own updated guidelines on trending news note that humans are still involved in the process of tweaking the algorithm at work. But as Quartz reported, the editorial staff that once guided the trending process has been replaced by Facebook engineers. Those engineers only determine whether trending topics are a duplicate of another topic, and whether they represent a “real-world news event.”

Ever since those changes, The Intersect has been tracking what Facebook trends, day-to-day, to see what stories one of the most powerful tech companies in the world is marking as important. You can follow along here, with our newsletter.

This post has been updated to include a statement from Facebook. 

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