A popular blog that lists “potential, possible, or probable predatory” publishers and journals has disappeared, but it is not clear why.

The blog—started in 2010 by librarian Jeffrey Beall of the University of Colorado in Denver (CU Denver)—now states: “This service is no longer is available.”

Beall declined to comment. But a CU Denver spokesperson told Science Insider that Beall made a “personal decision” to take down his list of low-quality journals that charge authors a fee to publish, often with little or no review or editing. The spokesperson says the blog was not hacked, nor was it taken down as a result of legal threats, and Beall will remain on the school’s faculty. The spokesperson could not confirm whether the blog's removal is permanent.

“I'm surprised and concerned,” says pseudonymous science blogger Neuroskeptic. “Beall's list is (was?) extremely valuable because predatory journals are a huge problem.”

Some are circulating a cached version of Beall’s list on Twitter. Others speculated on social media that the shutdown may have something to do with the transfer of its lists to the company Cabell’s International in Beaumont, Texas. But the firm has publicly said it is in “no way involved” with the blog’s closure. Nevertheless, Cabell’s noted that it has been developing its own blacklist, working with Beall as a consultant, since 2015, and plans to launch it later this year.

Lacey Earle, vice president of business development at Cabell’s International, tweeted that Beall “was forced to shut down blog due to threats & politics.”

Some entries in Beall’s lists did divide academics. One point of controversy was the addition of Frontiers—which is partly owned by The Holtzbrinck Group in Stuttgart, Germany, that also owns a share of the publishing giant Springer Nature—in 2015.

Earlier this month, Beall released an updated version that raised the number of questionable publishers to 1155 and problematic standalone journals to 1294.

Beall also maintained two other lists of “misleading metrics companies” and “hijacked journals.” Both are now unavailable.

With reporting from John Bohannon.