Some 10,000 panicked residents fled the city of Wenzhou, Zhejiang Province after a toxic gas leak on Tuesday caused babies to vomit, the China News Service reported.

Pungent gas began to spread about 9 pm on Monday in Lucheng district of the city, leaving nearby residents dizzy and babies vomiting, witnesses said.

Later the gas could be smelled in Huanglong district, closer to the urban area. As more and more people fell sick, panic poured onto the streets. Witnesses said at least 10,000 fled the district.

The environmental protection and safety supervisory departments identified the source of the leak at 2:30 am: a dye factory of Wenzhou Chemical Plant.

According to a director of the factory, they had found the leak of chlorine hydride from a valve at 11 pm Monday and turned it off. The valve was not completely shut down and the leak continued for hours without being noticed.

Local fire and environmental departments helped the factory stop the leak and used water spray branches to absorb the toxic gas still in the air.

In another development, police have began to investigate the causes of a chlorine gas leak in Guizhou Province on June 17 that led to scores of students being rushed to hospital, with 24 remaining sick and under observation.

Initially 175 children were hospitalized in Tongzi county after the Zunbao Titanium Plant discharged excessive chlorine gas in an event of equipment failure during trial operations on June 17.

The plant was shut down and has transported all its liquid chlorine away as of on Tuesday, according to Zeng Runyun, deputy secretary of the county committee of the Communist Party of China.

The plant's general manager and the person in charge of environmental protection have been removed from their positions.

The plant had made a public apology on June 25, Zeng said.

Dead fish were spotted in the creek near the plant on June 22. Tests show that the fish died from waste discharged by the plant.