Central China's Hubei Province is to launch a safety overhaul of its hazardous chemical industry following Wednesday's ammonia leak that killed one person, left six others ill and forced the evacuation of 20,000 people from their hoes.

The overhaul will focus on pressure vessels, pressure pipes and facilities to treat contaminated water, which have been blamed for the liquid gas leak, according to a circular issued on Friday by the Hubei Provincial Administration of Work Safety.

The accident occurred around 7:50 a.m. on Wednesday in a nitrogen fertilizer factory in Dawu County when an ammonia pipe broke.

A factory worker died at the site. Those taken ill included three factory workers, a fire fighter, a 16-year-old middle school student who was on her way to school at the time, and a pregnant woman in a nearby village.

All are in stable condition and receiving treatment in a local hospital.

The 20,000 residents who were evacuated have returned to their homes, local authorities have said.

About 10 tons of ammonia gas leaked, and fire fighters sprayed water into the air in shifts to dissipate the gas. However, the water flowed directly into the Huanhe River, where the factory is located, resulting in temporary high levels of ammonia and nitrogen in the river and threatening the safety of water use downstream.

The local government has discharged water from two reservoirs upstream to dilute the river water.

By Wednesday afternoon, the contents of ammonia and nitrogen in the Huanhe River had dropped, local environment authorities have said.

(Xinhua News Agency November 4, 2006)