This paper studies the role of Sina Weibo (a Chinese equivalent to Twitter) in disseminating vital information among the general public after the Wenzhou train crash in July 2011. Consuming low bandwidth while being capable of broadcast, information sent via micro-blogging can be quickly disseminated among a large population and provide first-hand accounts of the disaster. Micro-blogging seems therefore an ideal tool in the case of emergency news dissemination. Meanwhile, Weibo’s social network nature enabled information sent via Weibo to be used in pleas for help, in searching for dislocated people, and in the coordination of rescue efforts, as well as in voluntary activities. During the Wenzhou train crash, due the political nature of the incident, Weibo was also used as a platform for channelling public opinion, and it featured criticism of the official rescue efforts. This paper argues that Weibo’s strength in crisis communication lies in its real-time streaming of facts, perspectives and opinions, and in its reach. In this sense, Weibo adds new dimensions to the understanding of Web 2.0 technologies in emergency communication and shows potential for redistributing power among the government, the officially controlled news media, and citizen media.