Three remaining chlorine gas tanks at the Tianyuan Chemical Plant in southwest China's Chongqing Municipality where chlorine leaks and blasts killed nine on Friday were detonated yesterday.

Firefighters rushed into the plant to spray foam so that chlorine gas could be diluted.

Before the detonation mission was carried out, firefighters had already been spraying foam and alkaline water to dilute and counteract the chlorine gas, Xinhua reported.

After the detonation, people who had been evacuated from areas around the plant were informed to go back to their homes, the report said.

And environmental monitors entered the plant to test the air and water quality.

After the gas leak and blasts, the municipal environmental protection administration and water supply group kept monitoring the air and water quality in Chongqing.

Sources said that the air quality was normal Sunday morning, and nothing abnormal was found in the downstream section of the Jialingjiang River near the chemical plant.

In addition, a team investigating the incident, led by Chongqing Vice-Mayor Zhou Mubing, will look into the accident.

The decision to detonate the tanks was made in order to prevent the tanks from leaking chlorine gas.

Armour-piercing cannon fired by tanks were used to accomplish the mission after the failure of two machine gun shots and nine bazooka shots, Xinhua reported.

The accident on Friday killed nine people and injured three others.

More than 150,000 residents were evacuated from the areas surrounding the plant after toxic fumes from the chlorine filled the air.

According to a Xinhua report, 30,000 evacuated residents have returned home by 6:30 pm yesterday.

There were still 20,000 people who did not spend Saturday night at home.

The chlorine leak began Thursday night at the Tianyuan Chemical Plant in Jiangbei District and was followed by powerful explosions Friday afternoon, releasing a high concentration of highly irritating, greenish-yellow chlorine gas.

The fumes could be smelled in areas about 300 meters from the plant. Inhaling the gas at a density of 2.5 milligrams per square meter is enough to cause death and symptoms, including bronchial spasms, dropsy and respiratory difficulty.

Violations of operating rules by workers and outdated furnaces may end up being blamed for the chlorine leaks and explosions, sources say.

Meanwhile, five sectors have been for the first time ordered by the State Administration for Work Safety to improve their safety measures.

According to the Beijing Youth Daily, the five sectors are non-coal mines, manufacturers and traders of hazardous products, construction companies, agricultural transports and railways.

Coal mines and other four sectors received the warning from the administration in 2001 for their poor safety records.

(China Daily April 19, 2004)