21.   It was not known what caused her injuries.

22.   It was not known what caused the blast, and officials did not immediately comment.

23.   It was not known what caused the cargo train to derail.

24.   It was not known what caused the freight train to derail.

25.   It was not known what caused the jetfoil, a high-speed ferry with fins that push the craft over the water, to hit the submerged object.

26.   It was not known what caused the screams.

27.   It was not known what caused the train to derail.

28.   It was not immediately known what caused the blast although news reports cited firefighters as saying it may have been due to a gas leak.

29.   It was not immediately known what caused the collapse of the two-story building, where both the waiting and parcel rooms were located.

30.   It was not immediately known what caused the van to leave the narrow country road and crash through the wall.