Chinese ships are racing to clean up a giant oil spill after an Iranian tanker sank in the East China Sea. The 120 sq kms oil slick is thought to be made up of heavy fuel that was used to power the vessel. The Sanchi oil tanker sank yesterday and officials say all its crew members are dead.<br/><br/>It was carrying 136,000 tonnes of ultra-light crude oil from Iran which generates a toxic underwater slick that would be invisible from the surface. Both the fuel and the ultra-light oil could cause devastating damage to marine life.<br/><br/>The Sanchi and a cargo ship collided 260 kms off Shanghai on the 6th of this month, with the tanker then drifting south-east towards Japan. It caught fire after the collision and burnt for more than a week before sinking off China's east coast. Iranian officials now say all 32 crew members – 30 Iranians and two Bangladeshis – on the tanker were killed.