A 1-kilometer stretch of the Quxi River in Wenzhou, Zhejiang province, turned white on Monday as emulsion leaked into the tributary from a nearby chemical factory.

The emulsion was not toxic, but environmental experts said the discharge damaged the river.

"The pollutant was identified as natural emulsion, and the factory related (to the case) was shut down temporarily for further investigation," said Dai Dongpeng, a senior officer of the environmental protection bureau in Ouhai district, where the polluted river is located.

The leak occurred on Sunday evening after a liquid-transportation pipeline of natural emulsion ruptured at the Dashulin Trading Co, a local chemical-products supplier.

"About 200 kilograms of emulsion had flowed into the river before we noticed, which was too late," said Dashulin owner Zhang Jianhua.

Zhang added that the natural emulsion, which he had bought from Hainan province, was totally natural and not toxic.

A temporary dam was quickly built on Monday to prevent further water pollution in the river.

"The milk-white natural emulsion contained no biochemical toxicity, but it polluted the river and brought inconvenience to the daily life of local residents," Dai said.

Dai added that Zhang's company hadn't applied for the environmental approvals for setting up the transportation pipeline of natural emulsion, and his factory cannot be reopened until he submits the application.

He also said that the company that caused the incident will be fined.

Environmental experts said the incident had damaged the quality of water by turning it white.

"Even if the pollution source is the natural emulsion, which is not toxic at all, the clarity of natural water has been destroyed, as the suspended solids in the river was definitely over the standard," said Wu Jun, a professor at the School of Environment at Nanjing University.

Wu added that setting up the temporary dam to stop the flow of polluted water is the quickest way to prevent the expansion of the pollution, and the polluted water should be drained immediately for treatment.

By early Tuesday, the polluted water in the river had been pumped out and transformed to local sewage-treatment plants for further examination and treatment.

Shao Chenfang contributed to this story.

yuran@chinadaily.com.cn