11.   A preliminary investigation concluded that the explosion occurred in a closed area of the mine when accumulated gases were ignited by self-igniting coal.

12.   An electric spark was believed to have ignited gas that had built up in the basement of the building, the ministry said.

13.   DeFosset said there was an explosion Sunday afternoon after a cave-in hit electrical equipment and ignited methane gas.

14.   Electricity to the Morasha junction north of Tel Aviv was cut for fear a spark could ignite the gas, police said.

15.   Falling rock struck a battery generator, creating sparks that ignited methane gas, Hall said.

16.   If the fluid is too low, it can expose electric plates and ignite gases inside.

17.   It can explode there, or a carelessly lit match or electric spark can ignite the gas on the way into the stove.

18.   It was not yet known what ignited the gas.

19.   It can explode there, or a carelessly lighted match or electric spark can ignite the gas on the way into the stove.

20.   Recovery crews were close to the area by Thursday afternoon, but paused out of fear that drills and other rescue equipment could ignite gases and cause another explosion.