Thousands of people were evacuated on Friday as toxic fumes following a chlorine leak filled the air in Jiangbei District of southwest China's Chongqing Municipality, officials and eyewitness said.

To date, about 10 workers at the Tianyuan Chemical Industry Plant, where the accident happened, have reported minor respiratory symptoms but are not in danger, said Miao Guangkui, head of the rescue team at the scene said.

A large amount of chlorine gas was released into the air beginning late Thursday night when a leakage accident occurred at the city's Tianyuan Chemical Industry Plant. Minor explosions were recorded later, said Vice Mayor Zhou Mubing, who guided the rescue work at the scene.

All residents living within one kilometer of the spot and some citizens living in an urban area facing the plant on the other side of Jialing River were evacuated, Zhou said.

"At least 4,000 people were forced to leave," said a driver who helped move people away from nearby areas.

It was the third chlorine gas leakage at the plant since last year, said a worker at the plant, who declined to be named. Sources said the municipal government planned to move the chemical plant employing about 2,000 workers from downtown areas to Wanzhou District, a new city zone located in the Three Gorges Reservoir area.

The pressure inside the chlorine furnace dropped to 0.25 kilogram per square centimeters from 1.5 kilograms per square centimeters after experts discharged half of the liquefied chlorine in three furnaces.

"The emergency has been basically solved," said Miao Guangkui, head of the rescue team.

Local residents will have to wait until 18:00 Friday after the area is declared totally safe again, rescue workers said.