HANGZHOU - A chemical firm in East China's Zhejiang province is being investigated on suspicion of discharging waste that may have polluted a local river and disrupted tap water supplies since Sunday.

Zhejiang Jinzhili Chemicals Co Ltd in Zhejiang's city of Lin'an is suspected to have contaminated the Tiaoxi River with 12 volatile pollutants, including benzene and alkene, the environmental protection bureau in the provincial capital of Hangzhou said in a statement Wednesday.

The statement said that the bureau is working with public security authorities to investigate the case.

The pollution has disrupted the operation of two downstream water treatment facilities and affected tap water supplies in Hangzhou's Yuhang district, which has a population of about 848,400.

The Pingyao Waterworks, which treats water from the Tiaoxi River and supplies drinking water for the nearby towns of Pingyao and Liangzhu, halted operation on Sunday.

The local government has sent water trucks to the towns to distribute drinking water. Schools and kindergartens in the towns have been closed since Tuesday.

The city's Yuhang Waterworks had to temporarily halt operations before finding an alternative source of water, the Qiantang River.

More than 120 companies in Lin'an have halted production because of water shortages. An upstream reservoir has discharged more water to dilute the pollution.

An environmental monitoring report issued Wednesday morning said that no more pollutants have been detected in the Tiaoxi River, but it is unclear when the local waterworks will resume operations.

The investigation of the chemical firm comes on the heels of a carbolic acid leak that polluted Zhejiang's Xin'an River on Saturday.

The river, a major source of drinking water in Zhejiang, forced the temporary closure of five water utility companies.

Hangzhou residents were buying bottled water in a panic on Tuesday following the news of the two cases of contamination.