A recent chemical spill in the Xin'an River, a major source of drinking water for east China's Zhejiang Province, will not affect supplies of drinking water in the region, the local environmental protection bureau said on Monday.

The river's concentration of carbolic acid (phenol), an industrial chemical used to create plastic and other materials, has dropped because discharges of water in the upper reaches of the river have diluted the chemical, according to the bureau.

Authorities have been closely monitoring the river since late Saturday night, when a tanker truck damaged in an accident leaked the chemicals, which were washed into the river by heavy rains.

Water quality monitoring results will be publicly released soon, the bureau said.

According to water quality tests from Sunday evening, water in the provincial capital of Hangzhou was still safe to drink and had not been contaminated by carbolic acid, the local government said in a press release Sunday night.

Hangzhou's water utility companies are working on storing clean water to be dispensed later in case of contamination, the press release said.

The Xin'an River, which feeds into the Fuchun and Qiantang rivers, is the primary source of drinking water for several cities in Zhejiang, including Hangzhou.

Carbolic acid and its vapors are corrosive to the eyes, skin and respiratory system. Skin contact with the substance may cause burns. It can also harm the central nervous system, heart, lungs and kidneys.