How can consciousness arise without the fuel?
This question that I had asked is relevant to this question.

According to MN9:


  From the origination of fermentation comes the origination of
  ignorance. From the cessation of fermentation comes the cessation of
  ignorance. .....
  
  From the origination of ignorance comes the origination of
  fermentation. From the cessation of ignorance comes the cessation of
  fermentation.


To answer your question, ignorance is the cause. But to break the cycle, craving must be uprooted through the Noble Eightfold Path.

Also see Andrei's answer on the vicious cycle.