Chinese authorities stepped up their efforts to disperse a major oil slick in the Yellow Sea by mobilising 800 fishing boats to help the clean-up operation. The flotilla will join the 24 specialist ships that have been spraying dispersal agents, soaking up crude with panels of absorbent felt and using a floating barrage to prevent the slick from contaminating the beaches near Dalian. Investigators have also launched a probe into the pipeline explosion that caused the seepage and has subsequently forced the authorities to restrict access to Dalian Xingang oil terminal. A 300,000-tonne crude oil tanker, owned by Singapore Pacific Petroleum which was unloading its cargo at the time of the accident, has been held for checks. Officials said the dispersal operation was making progress despite rough seas. Considerably smaller in scale than the BP leak in the Gulf of Mexico, the slick has reportedly shrunk by more than a third from its peak of 50 square kilometres. But local reporters said the crude was evident on nearby beaches, where patches of sand and rocks were coated in a layer of oil.