Photo taken on April 11, 2014 shows the site of the source of the contamination which has caused excessive levels of benzene in tap water in Lanzhou, capital of northwest China's Gansu Province. Tests at a water plant at 8:30 a.m. on April 11 showed tap water contained 160 micrograms of benzene per liter, far in excess of the 10 micrograms per liter national limit, according to the city's environmental protection office. An initial investigation found problems in a 3 km channel that links the plant that preprocesses the water and the plant that supplies water to Lanzhou. (Xinhua/Chen Bin)

Staff members of several departments work near the site of the source of the contamination which has caused excessive levels of benzene in tap water in Lanzhou, capital of northwest China's Gansu Province. Tests at a water plant at 8:30 a.m. on April 11 showed tap water contained 160 micrograms of benzene per liter, far in excess of the 10 micrograms per liter national limit, according to the city's environmental protection office. An initial investigation found problems in a 3 km channel that links the plant that preprocesses the water and the plant that supplies water to Lanzhou. (Xinhua/Chen Bin)