It’s the 32nd anniversary of the infamous 1989 Tiananmen Square massacre, in which Chinese troops opened fire on and slaughtered hundreds of pro-democracy protesters in Beijing.

The Chinese government does not like talking about it, and it does not like it when others do. It is near the top of a long list of topics that state censors have blacklisted in Chinese media and on the internet, and that companies and other nations that do business with China are under pressure not to bring up. One image, a world-famous photograph of an unknown individual dressed in business attire standing in the way of tanks rolling in to suppress the protests known as “Tank Man,” is especially sensitive. So it’s odd that searching for that image on search engines Bing, Yahoo Search, and DuckDuckGo from within the United States yielded no results on Friday—something Microsoft quickly fixed.

Throughout the afternoon on Friday, using the image search function on Microsoft-owned Bing with the words “Tank Man” yielded the message, “There are no results for tank man / Check your spelling or try different keywords.” (According to Motherboard, the same is true in other countries other than the United States, such as France and Switzerland.) “We did not find results for: tank man,” according to Yahoo Search, which is powered by Bing. Attempt the suggestions below or enter a new query above.” DuckDuckGo’s results simply stated, “Sorry, no results here.” Some, such as veteran Reuters cybersecurity reporter Joseph Menn, saw this as evidence of China’s clout over foreign tech firms that do business with Chinese firms.

It’s especially strange because using the general search function (not image-specific) for “Tank Man” on all three engines yields reams of information, including thumbnails of the photo. Using the image search function with the more specific “Tank Man Tiananmen Square” query returns numerous images on Bing and DuckDuckGo, but only 17 results on Yahoo image search.

Microsoft has had a presence in China for decades, and Bing is available there Like competitors such as Apple, the company has long catered to the whims of Chinese censors in order to maintain access to the country’s massive market, and it purges Bing results within China of information deemed sensitive by the Chinese government. However, the company stated that the blocking of image results for “Tank Man” in the United States was not intentional and that the problem was being addressed.

“This is due to an unintentional human error, and we are actively working to resolve it,” a Microsoft representative told Gizmodo via email. Searching for “Tank Man” on Bing returns many results as of early Friday evening, though the famous photograph appears only in passing in the form of a desktop wallpaper heavily modified to obscure the tanks.

One possible explanation for all three sites having the “Tank Man” problem is that smaller search engines lack the scale to index the web themselves and must instead license their indexes from Microsoft. Yahoo’s image results for the query were identical to Bing’s updated version as of Friday evening.

DuckDuckGo is blocked in China and thus appears to have little incentive to censor, despite the fact that it partners with both Yahoo and Bing, from which it licenses its index. As of early Friday evening, its results appeared to be in the process of being updated.