1.   Habibubullah Allahyar, a senior official at the Afghan consulate in Quetta, Pakistan, said it was not known what triggered the initial blast.

2.   It is not known what triggered the illness.

3.   It was not immediately known what triggered the explosion.

4.   It was not known what triggered the collapse.

5.   It was not immediately known what triggered the incident, but derailment might have been the cause, said Holdert.

6.   It was not immediately known what triggered the fire that engulfed part of the area.

7.   It was not known what triggered the clash, but there is a long history of ethnic tensions between south and north Vietnamese in Hong Kong centers.

8.   It was not known what triggered the clash, but there is a long history of ethnic tensions between southern and northern Vietnamese in Hong Kong centers.

9.   It was not immediately known what triggered the latest violence, although the two clans have clashed repeatedly over the past two months over a misundertanding.