Cloud-storage site Dropbox has been blocked in China, only four months after access was restored to internet users in the the world's most populous country.
Both the Dropbox app and the web-based service have been affected by the block, which came into effect yesterday according to online censorship monitor GreatFire.
Dropbox was first banned in China in 2010 after a worldwide surge in popularity. In February of this year it was made available again without warning or explanation.
The latest ban appears to be more severe than the first, which previously allowed access to some Dropbox-related services. Dropbox is yet to respond to a request for comment on the matter.
Other major websites to have been hit by China's strict internet censorship - often referred to as the Great Firewall of China - include Google, Facebook, Yahoo and Amazon, as well as major media outlets like Reuters, the Wall Street Journal and the Guardian.
Users vented their frustration on Twitter over the blockage, with some requesting suggestions for similar sites that are accessible in the country.
Google Drive, a file-storing service that performs a similar function to Dropbox, has been banned in China since it was launched in 2012.
Other China-based equivalents, such as Baidu's WangPan and Tencent's WeiYun, are still operational and offer vastly better storage options than their foreign equivalents.
Tencent, for example, offers users 10 terabytes of free storage - over 500 times more than the 2GB offered by Dropbox.