Crude oil leaking from a petrochemical pipeline of CNPC, China's largest oil company, caused hazardous levels of benzene in a northwest Chinese city's tap water, it was confirmed yesterday.

Residents in Lanzhou collect free water yesterday bottled by a local company using spring water sourced from a mountain area. By last night, the city’s tap water was deemed safe. [Photo/Xinhua]

Polluted water ran through aged joints in a concrete channel between two water works owned by Veolia ,a joint Sino-French venture in Lanzhou, leading to excessive levels of the chemical, Wang Jinsheng, a member of the national environmental emergency panel, said yesterday.

There had been several oil leaks at the Lanzhou Petrochemical Company, a subsidiary of CNPC, in the 1980s, said Wang, a professor at Beijing Normal University's College of Water Sciences, told Caixin.com.

The channel has been carrying water to Veolia Water's No. 1 and No. 2 plants for decades and the oil pipeline lay under the channel. The company is the sole water supplier for urban Lanzhou.

Crude oil was found in soil about a meter below the channel, Wang said.

On its official microblog yesterday, the Lanzhou government confirmed that the high levels of benzene were caused by oil pollution in surrounding areas, but gave no further details.

The local government said residents in more than 80 houses above the polluted channel would be relocated in the near future, according to the Oriental Morning Post.

A relocation and compensation scheme had not yet been worked out but the residents had all agreed to move, the newspaper reported yesterday.

Earlier, Yao Xin, Veolia's president, told the Beijing News that the petrochemical pipeline under the 60-year-old channel had leaked oil in the 1980s, but instead of being replaced it had been repaired and was still in use.

According to the Oriental Morning Post, some of Lanzhou Petrochemical's oil pipelines had been in service for more than 50 years.