premise: China's Ministry of Public Security on Tuesday urged police to learn from a fatal bus crash in northeast China and launch safety inspections of schoolbuses.
  Eight children were killed when a bus carrying 50 students veered off a bridge and plunged into a frozen river last Tuesday in Zhoujia township of Shuangcheng City, Heilongjiang Province. Thirty-nine others were injured.
  In a circular issued by the ministry, local police bureaus were required to launch immediate examinations of all vehicles and drivers involved in school transport.
  All vehicles and drivers must be registered with the local education authorities, and those with potential safety risks must be removed from service immediately, according to the circular.
   Why is China launching safety inspections of its school buses?
hypothesis: a fatal bus crash in northeast China