A large tent measuring up to 20,000 square meters is erected over the site of an obsolete pharmaceutical plant in Hangzhou, Zhejiang province, on Tuesday. The soil under the tent is said to be highly toxic. Lian Guoqing / For China Daily

A huge tent was put up over the former site of an insecticide factory in Hangzhou, Zhejiang province, to contain a peculiar smell emanating from polluted soil, local news website zjol.com.cn reported.

The tent in downtown Hangzhou covers about 20,000 square meters and is 36 meters high.

It was built on top of where Hangzhou Qingfeng Agricultural Chemical once stood. It was relocated in 2009, but the more than 50-year-old company left many contaminants buried in the ground.

Following an investigation and risk assessment, treatment of the polluted soil was initiated in September.

However, in the process of the treatment, a peculiar smell was released, seriously affecting nearby residents.

A woman surnamed Shao, who lives two bus stops away from the site, said she can still smell a pungent odor.

"We can only lighten the smell by stuffing clothes into the cracks between the window frames. We dare not open the windows or hang clothes out to dry. We also stopped going out for walks in the evening," she said.

Another woman who lives next to the site and identified herself only as Xu told the news website on Tuesday that the odor is still strong in the evening and that she didn't think the tent did much to prevent the smell from spreading.

A woman surnamed Shen from Hangzhou Industrial Investment Group, who now owns the property rights to the polluted land, said the company conducting the treatment has taken measures to remove the peculiar smell, such as injecting deodorant into the soil before turning it over.

She also said the company has conducted a series of experiments and also sent some samples of the soil and underground water to institutes in Beijing and Shanghai for analysis to improve the effects of the deodorization process.

Shen Dongsheng, a professor with the School of Environmental Science and Engineering at Zhejiang Gongshang University, said the pollution is a result of the insecticide factory's poor eco-friendly practices.

"They buried a lot of production waste and seriously polluted the soil with toxic organics," he said.