11.   Police said a trip wire attached to the front door and the grenade had triggered the blast.

12.   A jury agreed Friday with Patrick Horan that an improper gap in a switchboard triggered the blast.

13.   Any vehicle too wide for the passageway would be destined to bump the wall and trigger a blast.

14.   Emergency officials said they had not determined what triggered the blast.

15.   He said the blast was triggered by remote control.

16.   Investigators had not discovered what triggered the blasts.

17.   It was unclear what triggered the blast, although some witnesses said it may have been a land mine.

18.   It was unclear what triggered the blast, although some witnesses said someone may have triggered a land mine near a structure where the ammunition was being handled.

19.   Mine blasts are often triggered when digging miners strike a pocket of flammable gases trapped in rock.

20.   Navy officers said it was not clear what triggered the blast, but speculated that an electrical short-circuit may have ignited the fuel tank.