Chinese environment officials are rushing to build three temporary barriers on the Yellow river after failing to contain an oil slick in a tributary of the country's second largest waterway. Despite overnight efforts by 700 workers to dig diversion channels, the contamination belt � which was 13 miles long at its peak � has tainted the giant Sanmenxia reservoir, the state media reported. Some areas have been forced to suspend water supplies as the spill spread from the Wei tributary in Shaanxi province to the Yellow river in Henan province. The oil spill occurred when 150 tonnes of diesel leaked from the Lanzhou-to-Chengsha pipeline owned by the China National Petroleum Corporation. After the leak, the state-owned firm and environment ministry dispatched teams to the area to try to control the leak before it entered the Yellow river, which sustains 140 million people with water supplies for drinking, irrigation and industry. As well as diversion ditches, they used 27 floating barriers to try to isolate the diesel so that it could be removed or soaked up with absorbent materials. The Sanmenxia dam has been closed to prevent the contamination from passing further downstream. Emergency teams are using the floating barriers to divert the spill to an area of the reservoir where it can be dealt with. The Yellow, often described as the Cradle of Chinese civilisation, is one of the country's most heavily exploited and polluted rivers. According to the United Nations, water is unfit for any use along one third of the river.