Well, that was brief. Back in February, Dropbox was found to have been unblocked in China, but now it seems that the popular cloud-storage service is no longer accessible in the the world’s largest country, according to tweets from users and data from censorship monitoring organization GreatFire.org.

The GreatFire database, which continually tests the accessibility of internet links from inside China to identify new blockages, shows that dl.dropbox.com (used for downloading files) is no longer accessible from inside China, which suggests that its apps will no longer work. In addition, the main Dropbox.com appears blocked there too, according to the organization’s analytics.

Since GreatFire monitors web-based URLs and not the performance of apps, it isn’t entirely clear how the apps will perform. That said, GreatFire tells TNW that it believes the entire Dropbox.com domain has been ‘poisoned’ — that’s the “strictest method of blocking” which theoretically impacts app performance in China.

Regardless of the technical details, users are voicing frustration with the change in Dropbox’s performance in China today.

The reblocking of Dropbox, which recently passed 300 million registered users worldwide, comes during China’s most severe crackdown on Google’s services to date. Gmail, Google Maps, and other Google services have been entirely blocked in China since early June, in conjunction with the 25th anniversary of the Tiananmen Square protest on June 4.

While it is common for China to surpress overseas internet services and their users around the anniversary, which is one of the most controversial dates in the country’s history, it is unprecedented for the clampdown to last for nearly four weeks, as is the case right now.

Speaking using a pseudonymn, one GreatFire founder told TNW that the organization believes China’s blocking of Google and the reversal of its policy on Dropbox shows the country “is willing to crack down on other foreign services more harshly than ever.”

The founder went on to explain that this particular block on Dropbox seems more serious than before. While the previous block prevented users from accessing Dropbox.com, they were able to use desktop apps to some degree during that period — this time around, however, the GreatFire founder believes all Dropbox-related services could be blacked out in China.

We’ve contacted Dropbox for comment, and will update this post with any additional information that we receive.