Violations of operating rules by workers and outdated furnaces could be blamed for the chlorine leak and explosions that killed seven people and injured three others Friday afternoon in southwest China's Chongqing Municipality, an expert said.

"The gas leak was largely due to the outdated furnaces and other equipment," said Miao Guangkui, head of a technical team at the scene. "But malpractice by workers after the leak caused the explosions."

To date, at least seven people were killed and three others injured by the explosions Friday afternoon at the city's Tianyuan Chemical Industry Plant, where chlorine gas started leaking Thursday night, said local work safety officials.

According to the original emergency treatment program, the liquefied chlorine gas would be discharged through steel pipes under natural air pressure.

But the technical team suspected that workers at the plant usedthe machine to draw chlorine gas from the furnaces to speed up theprocess, which led to explosions following the abrupt temperature rise inside the furnaces, Miao said.

More than 150,000 residents have been moved out of areas surrounding the plant as toxic fumes from the chlorine leak have filled the air.

The highly irritating, greenish-yellow fumes can be smelt 300 meters from the plant. Inhalation of 2.5 milligrams of chlorine gas is enough to cause death and symptoms of inhalation include bronchial spasms, dropsy and respiratory difficulty.

Some 100 armed policemen have been mobilized to keep order and withdraw the residents. Officials said more than 600 officers and soldiers are now in their combat readiness to reinforce rescue efforts any time.

Chongqing Mayor Wang Hongju also went to the scene after the explosions.

Investigation and evacuation are still underway in Chongqing, the biggest city in southwest China.

It was the third chlorine gas leak at the plant since last year,said a worker at the plant, who declined to be named.

Source: Xinhua