Due to the inadequacy of official notices in disseminating retraction information, a significant proportion of retracted articles continue to be cited in the post-retraction period. There are adverse consequences of citing such questionable articles. This study extends the literature on official versus unofficial information channels by examining three key roles that unofficial information channels can play in disseminating retraction information (i.e., providing broader reach for information dissemination, packaging information from different sources, and creating new information) as well as the effects of these roles. An unofficial information channel affords a broader reach for information dissemination, which reduces post-retraction citations. Moreover, according to the information processing theory, different types of additional information (that comes from the ability of an unofficial information channel to package information from different sources or create new information) can moderate such effect. Leveraging on the launch of Retraction Watch (RW), an unofficial information channel for reporting retractions, this study designed a natural experiment and found that reporting retractions on RW significantly reduced post-retraction citations of non-swiftly retracted articles in biomedical sciences. Furthermore, additional author-related and retraction-related information provided on RW enhanced the main effect, whereas additional article-related information provided on RW weakened the main effect.