LANZHOU, March 5 -- The government of the northwestern Chinese city of Lanzhou announced on Wednesday night the tap water in the city is safe for drinking following rumors of contamination.

The ammonia nitrogen index of the Lanzhou Veolia Water Company, a Sino-French joint venture and the sole water supplier for urban Lanzhou, conforms to the national standard, according to a government statement.

The tap water is safe for drinking and there is no contamination, it said.

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

"There is an ammonia nitrogen odor and it smells very bad," said a resident with the surname Qi.

"It has a bitter taste and we will stop using tap water," she said.

The Lanzhou government will scrutinize factories along the Huangshui River and investigate the cause of odor. It will strengthen the clearing of algae and dead leaves, which are likely to be behind the odor, according to the statement.

The government also ordered the Lanzhou Veolia Water Company to use activated carbon to purify the water and ensure water quality, it said.

Tap water contamination caused by outdated water ducts affected 2.4 million people in Lanzhou last April.