Authorities in China are using more than 23 tonnes of oil-eating bacteria to help clean up an oil spill in the Yellow Sea caused by a pipeline explosion and fire at the weekend, state media said on Tuesday.

Yang Jiesen, head of the research and development division of a Beijing biotechnology company, said the Maritime Safety Administration had placed its order for the bacteria on Saturday, the official Xinhua news agency reported.

Dozens of oil-skimming vessels and hundreds of fishing boats were working to remove the slick off the northeastern port city of Dalian, after the accident on Friday that spilled an estimated 1500 tonnes of crude into the sea.

“The use of the oil-eating bacteria at the Dalian spill is the first time China has made major use of biotechnology to solve an environmental pollution problem," the report said.

The process, known as bioremediation, uses microorganisms to break down some toxic hydrocarbons present in crude oil into less harmful compounds. It was used to help mitigate the 1989 Exxon Valdez oil spill in Alaska.

The Dalian incident has affected shipments of oil to southern China as the port has been partially closed, but refineries there are now processing inventories so oil prices are not expected to be impacted, Xinhua said.

Meanwhile, workers in Dalian are using oil barriers to prevent the slick from spreading, but are concerned wind and heavy rain could worsen the situation, it added.

So far, at least 460 tonnes of oil have been scooped up, according to the report, which gave no more details about the size of the spill.

According to previous news reports, the worst of the spill initially covered 50 square kilometres but had been reduced to 45 square kilometres as of Monday.

But Xinhua reported then that a dark brown oil slick had stretched over at least 183 square kilometres of ocean.