1.   These fields made the inner core spin faster, they found, much as moving magnetic fields in an electric motor cause its shaft to turn.

2.   The blast caused the shaft where the miners were working to collapse and also set off a fire in the mine that raged throughout the day.

3.   The explosion caused the shaft where the miners were working to collapse and set off a fire.

4.   But on Monday, several consecutive gas explosions ripped through that section of the mine, causing other shafts -- where miners were still working -- to collapse.