A man carries water supplied by the local government in a community in Lanzhou, capital of northwest China's Gansu Province, April 12, 2014. Tap water in downtown Lanzhou has been found to contain excessive levels of benzene, provincial authorities said on Friday. The local government has taken emergent measures to ensure the safe water supply in affected areas. (Xinhua/Zhang Meng)

Residents queue up for water supplied by the local government in a community in Lanzhou, capital of northwest China's Gansu Province, April 12, 2014. Tap water in downtown Lanzhou has been found to contain excessive levels of benzene, provincial authorities said on Friday. The local government has taken emergent measures to ensure the safe water supply in affected areas. (Xinhua/Zhang Meng)

Bottles of water are piled up in front of a store in Lanzhou, capital of northwest China's Gansu Province, April 12, 2014. Tap water in downtown Lanzhou has been found to contain excessive levels of benzene, provincial authorities said on Friday. The local government has taken emergent measures to ensure the safe water supply in affected areas. (Xinhua/Zhang Meng)

A local restaurant keeps bottles of water in reserve in Lanzhou, capital of northwest China's Gansu Province, April 12, 2014. Tap water in downtown Lanzhou has been found to contain excessive levels of benzene, provincial authorities said on Friday. The local government has taken emergent measures to ensure the safe water supply in affected areas. (Xinhua/Zhang Meng)

Local residents get water in a community in Lanzhou, capital of northwest China's Gansu Province, April 12, 2014. Tap water in downtown Lanzhou has been found to contain excessive levels of benzene, provincial authorities said on Friday. The local government has taken emergent measures to ensure the safe water supply in affected areas. (Xinhua/Zhang Meng)

Residents carry bottle water in a community in Lanzhou, capital of northwest China's Gansu Province, April 12, 2014. Tap water in downtown Lanzhou has been found to contain excessive levels of benzene, provincial authorities said on Friday. The local government has taken emergent measures to ensure the safe water supply in affected areas. (Xinhua/Zhang Meng)

Residents queue up for water supplied by the local government in a community in Lanzhou, capital of northwest China's Gansu Province, April 12, 2014. Tap water in downtown Lanzhou has been found to contain excessive levels of benzene, provincial authorities said on Friday. The local government has taken emergent measures to ensure the safe water supply in affected areas. (Xinhua/Zhang Meng)