1.   A fuel tank explosion has been blamed for only one other Black Hawk fatal crash.

2.   Hamas blamed the explosion on Israel and the PLO, although Palestinian police said the militants blew themselves up accidentally while preparing bombs.

3.   Russian military officials at the Mozdok air base, northwest of Chechnya, said the blast had unleashed a poisonous cloud and blamed the explosion on the militants.

4.   The explosion was blamed on a large pocket of natural gas that apparently seeped from an oilfield next to the campus and accumulated beneath the school building.

5.   The explosion was blamed on an electrical short.

6.   The explosion was initially blamed on a bomb, but there was also evidence of an accident.

7.   Those explosions were blamed on Chechen rebels, and led to a renewed military campaign in the breakaway republic.

8.   Those explosions were blamed on Chechens, and led to a renewed military campaign in the southern province.

9.   Police also blamed that explosion on Maoist insurgents who have been fighting for six years to abolish the constitutional monarchy in this Himalayan kingdom.