CHANGSHA - An oil spill has contaminated a river which is the source of drinking water for the Central Chinese city of Yiyang, forcing local authorities on Friday to cut tap water supplies to the city's 400,000 residents.

Oil leaked Thursday night from a oil-transport ship, which was traveling on the Zijiang River that flows through the city in Hunan province, polluting a source of tap water for the Yiyang Tap Water Plant, a spokesman with the municipal government said Friday.

To ensure the safety of drinking water for citizens, the local government decided to temporarily cut the city's water supply, the spokesman said.

In a notice issued Friday morning, the municipal government announced that authorities would provide citizens with the reserve supplies of clean water from 12 pm to 1 pm.

"Currently, the government is taking emergency measures to control the pollution to ensure the early resumption of water supply," the notice read.

"The government has set up a panel to investigate the cause of the pollution," it read.

The city government has offered an apology to its residents for the inconvenience.