已下令对最近的铁路灾难进行调查。

An inquiry was ordered into the recent rail ___disaster.

这是该地区有史以来遭受的最严重的自然灾害之一。

This is one of the worst natural ___disasters ever to hit the area.

一切进展顺利，直到灾难突然降临。

Everything was going smoothly until suddenly ___disaster struck.