The environmental departments have received reports of four accidents so far but they did not affect local water and air quality, he said.

Containers of liquid ammonia and vitriol were damaged and substances leaked at two chemical plants in Shifang City, Sichuan, one of the worst-hit cities, where a factory collapsed and about 100 workers were buried.

The State Administration of Work Safety (SAWS) said on May 13 that more than 80 tonnes of liquid ammonia had leaked in Shifang and the local government ordered the evacuation of more than 6,000 people.

At a food packinghouse in Qingchuan County, Sichuan, stockpiles of liquid ammonia, used for flash freezing, also leaked.

Technicians stopped the leak quickly and did not find serious damage to the local environment, Wu said.

He did not mention the dates or times of the three accidents.

The last case was an instance involving phosphorus (yellow) burns at a chemical plant in Hanwang County, Mianzhu City, another hard-hit place. The accident took place after the May 12 quake, the burning was contained on May 14 and the rest of the phosphorus was moved to safety on May 19.

The environmental monitoring network in the quake zone sustained extensive damage, Wu said. "It will be a tough task to maintain and supervise the local environment in the near future."

The latest figures the ministry received showed that more than 6,200 monitoring devices, 72 automatic monitoring stations for air and water quality and 934 environmental remediation facilities were damaged in the quake.

(Xinhua News Agency May 23, 2008)