China ? A stockpile of chemicals being used to disinfect an earthquake-shattered Chinese town ignited Thursday and injured scores of soldiers doing relief work, adding to a day of problems for urgent recovery efforts.

Heavy rain also added to the misery of crowds of homeless survivors living in tents or lean-tos, and hampered troops rushing to drain a quake-spawned lake before it floods a valley filled with villages.

The chemical fire took place in the town of Leigu, in devastated Beichuan county. The official Xinhua News Agency reported that more than 800 people were evacuated to avoid a cloud of dense chlorine gas caused by the blaze.

As in many destroyed towns, officials have been spraying disinfecting bleach on streets and rubble in an effort to prevent disease breakouts. Thousands of people are still missing and their bodies could be buried in the rubble, while rats and other scavengers have been reported in some places.

But one expert said the spraying of bleach on rubble has little effect except perhaps a psychological one for victims.