A diesel oil leak from a pipeline in northwest China's Shaanxi Province has been taken under control, said the pipeline owner, China National Petroleum Corporation (CNPC) on Saturday.

The company said it has immediately shut down the pipeline when the accident, which led to "large amounts of" diesel fuel leaking into the Chishui River, as well as the Weihe River - a major branch of the Yellow River, was discovered early Wednesday.

The Shaanxi provincial government said late Saturday the oil leaked from a branch of the Lanzhou-Zhengzhou-Changsha pipeline that transports fuel from the Northwest to the central regions amounted to about 150 cubic meters.

The leakage site was nearby the Chishui River in Chishui town in Huaxian County, 3 km upstream the Weihe River and 73 km upstream the Yellow River, the authorities said.

The company has built 23 blocking belts on the rivers and the local government built 3 more dams to prevent leaked oil from flowing into the Yellow River.

A 700-people crew has been working on the cleanup. So far, much of the leaked oil and polluted silt has already been taken away, according to the company.

Despite the cleanup, oil has been detected in the river water 33 km downstream the leakage site, the government said.

It added that it has warned the local residents not to use the river water directly as the leakage may pollute the Yellow River.

Preliminary investigation showed that the pipeline damage was caused by construction work of a third party, said the CNPC.

CNPC and the local government are closely monitoring water quality of the two rivers to prevent further environmental damage, so as to guarantee supply of safe drinking water to local residents.