Social media has become a popular platform of interpersonal communication in which users can search for news and convey real-time information. This study aims to investigate and analyse how Twitter has been used by its citizens during a massive international product recall to share and convey information. Based on the SMCC model and the Crisis Response framework, this study proposes a new crisis communication research model, namely Social-broadcasting Crisis Communication (SBCC), and uses it to analyse the 2016 Mars product recall dataset which formed of 10,930 Twitter messages. The study finds that the overall attitude of Twitter citizens towards the scandal was negative; the Twitter platform has mainly been used to spread the repetition of information from news media and ask questions; and the information diffusion (retweeting) has positive associations with the number of followers and the use of Hashtags. The findings suggest effective methods for organisations to supervise crisis communication and protect reputational assets during a crisis event (e.g., to pay more attention to Twitter citizens who have a large number of followers and how to disseminate information to control rumour-related information).