Breakthrough of bottleneck in investigations of group poisoning

Investigation bottleneck in this article is defined as the situation in which the investigation comes to a standstill period in which the hypotheses have been raised, but no more evidence can be collected to support them;or the findings are so little that a hypothesis can't not be generated; or the intervention measures,which have been taken based on the hypotheses, don't bring any expected results. According to our experience on several cases, how to break bottleneck during the investigation of group poisoning was discussed.