LANZHOU, March 7 -- Experts have concluded that the foul stench of tap water in northwestern Chinese city of Lanzhou was caused by bad water and decomposed waterweed flushed from neighboring Qinghai Province, Yu Haiyan, secretary of the city's Communist Party of China (CPC) committee, said on Saturday.

The rare odor and taste in tap water will go away by itself as upstream water supply increases in the capital city of Gansu Province, the experts said.

There had been public complaints of tap water pollution circulating online since Wednesday morning, causing panic buying of bottled water.

Lanzhou municipal government announced on Wednesday night that tap water in the city was safe for drinking following rumors of contamination.

On Thursday night, the local government said the rare odor and taste in tap water were reduced to some extent.

A team of experts from the Ministry of Environmental Protection, Ministry of Housing and Urban-Rural Development and Tsinghua University arrived in Lanzhou on Thursday.

Tap water contamination caused by outdated water ducts affected 2.4 million people in Lanzhou last April.