It will take at least three years to rehabilitate the water of a Yunnan lake to safe drinking standards after a serious arsenic leak, Xinhua News Agency reported on Friday.

Yangzonghai Lake, one of the nine major highland lakes in Yunnan, had waste water containing arsenic leaked into it from a plant in southwest China's Yunnan Province.

The incident polluted the drinking water source for more than 26,000 residents.

A local environmental protection agency first detected abnormal amounts of arsenic in the lake back in June. An investigation discovered that waste water from a riverside plant had soaked through piled toxic residue and then seeped into the lake due to an absence of waste treatment facilities.

The provincial authority has declared the lake's water unsafe for drinking, swimming and fishing. Alternative drinking water sources have been provided for local residents.

The polluter, Yunnan Chengjiang Jinye Industry and Trade Company Limited, was shut down and those responsible have been arrested.