Maritime workers in Dalian, a coastal city in northeast China's Liaoning Province, are still cleaning up a pollution belt at sea after fire was put out at an oil pipeline.

A dark brown belt of crude oil and other pollution stretches at least 50 square kilometers in seawaters off Dalian's Xingang Harbor.

About 20 vessels were cleaning the pollution Saturday, including four patrol boats from the provincial maritime bureau.

Large quantity of oil spill dispersant and absorption felt have been shipped in from Tianjin and the eastern Shandong Province, maritime officials said.

Fire engulfed the harbor Friday evening, after a blast hit an oil pipeline and triggered an adjacent pipeline to explode. Flames raged for 15 hours before they were extinguished Saturday morning. No casualties were caused.

"I heard a bang and felt as if someone had pushed me hard," said Chen Zhigang, an officer with Dalian border police who witnessed the accident. "For a moment I thought there was an earthquake."

The accident aroused the attention of China's top leadership, prompting instructions from President Hu Jintao and Premier Wen Jiabao. Vice Premier Zhang Dejiang rushed to the fire site Friday night to direct the rescue work.

The cause of the accident is still under investigation.

China's Central Television said the explosion happened when a 300,000-tonne Liberian tanker was unloading oil at the harbor. It said the tanker, carrying 27 sailors, left safely.

The pipelines were links between oil ships and oil tanks on land.

Dalian's downtown areas were overshadowed by smog Saturday. The environment authorities said hydrocarbon density was high within a radius of 1.2 km from the fire site.

There is no inhabitant within 3 kilometers from the site, but about 600 families live within 4 km.