premise: Nineteen people were killed and several others injured in a bus-truck collision in central Venezuela on Wednesday, said Venezuelan Deputy Director for Land Transportation Ivan Noguera.
  Noguera told reporters that the cause of the crash, which happened on a highway across a valley in the Miranda state, had not been finally determined. But he said the heavy rainfall hours before the accident could be blamed for the tragedy.
  Firemen, the National Guard and other rescuers were sent to the spot of the collision.
  According to a local fire brigade officer working at the scene, signs on the spot showed that because of overspeeding the bus lost control and swerved into the opposite lane, colliding with the truck carrying Coca Cola products.
   What caused the tragedy?
hypothesis: the collision