Officials in Yuxi , Yunnan , have arrested two chemical plant bosses over the arsenic contamination of Yangzong Lake, the third-deepest lake in the province, state media said yesterday. Jinye Industrial and Trade chairman Li Dahong and production team leader Jin Dadong were charged by the Chengjiang county procuratorate for alleged involvement in the serious pollution, Xinhua said. The procuratorate said the chemical plant, which makes fertiliser, was the main source of contamination in Yangzong Lake, about 30km east of the provincial capital Kunming and one of the nine highest lakes in Yunnan. At a media conference last month, provincial officials stressed that no one had died from the pollution. Earlier reports said the plant had used arsenic, known to cause skin cancer and other problems, and had failed to set up an impervious treatment system to prevent the chemical from permeating into nearby underground water. A great quantity of arsenic flowed into the lake through underground streams. Its presence was confirmed in June when many aquatic animals suddenly died. Authorities banned more than 26,000 villagers from drinking lake water, fishing or swimming, and 226 fishing families lost incomes. It is estimated that the tainted lake will need at least three years to recover. Yunnan media pointed to seven other chemical factories and tourism construction projects also to blame, but officials said Li and Jin's plant was the most serious offender.