For several hours today, Facebook blocked links to “bsdetector.tech,” the website for a popular browser extension that detects and tags disreputable news sources.

“This message contains content that has been blocked by our security systems,” an error message told users when they attempted to link to the site on Facebook. “If you think you're seeing this by mistake, please let us know.”

Daniel Sieradski, the creator of B.S. Detector, took to Twitter this morning to point out the problem:

It’s unclear why Facebook blocked the extension’s page, but it began working again this afternoon.

Created to correct for fake news floating around the web, B.S. Detector works by using a list of domains with known issues, and then flagging links to those sites. Categories like “fake news,” “state news,” and “conspiracy theory” appear next to the relevant links and pages.

The tool gained some accidental notoriety late last night, when TechCrunch erroneously reported the tool was a feature built by Facebook itself to detect fake news. TechCrunch later updated the story to note it was seeing B.S. Detector.

Facebook did not return a request asking for clarification on why the site was blocked. 

Update, 2:58PM ET : Facebook is again allowing links to the site.

Update, 12/3, 4:42PM ET: Facebook provided the following statement:

We maintain a set of systems to help us detect and block suspicious behavior on our site. We temporarily blocked people from sharing the domain bsdetector.tech because of other abuse we have seen from the .tech top-level domain. We have corrected the error.