Oil spill from sunken tanker trebles in size in East China sea

The spill from a sunken Iranian tanker off China's east coast has more than trebled in size, just over a week after the ship sank in a ball of flames.

Authorities spotted three oil slicks with a total surface area of 332 square kilometres (128 square miles), compared to 101 square kilometres reported on Wednesday, the State Oceanic Administration said in a statement late on Sunday.

The Sanchi, which was carrying 136,000 tonnes of light crude oil from Iran, collided with Hong Kong-registered bulk freighter the CF Crystal in early January, setting off a desperate race by authorities to search for survivors and stave off a massive environmental catastrophe.

The bodies of only three of the ship's 30 Iranian and two Bangladeshi crew members have been found. 

Three coast guard vessels were on the scene on Sunday night assessing the spill, the oceanic administration said.

The type of condensate oil carried by the Sanchi does not form a traditional surface slick when spilt, but is nonetheless highly toxic to marine life and much harder to separate from water. The cargo amounted to nearly one million barrels (bbl) of oil.

The area where the ship went down is an important spawning ground for species like the swordtip squid and wintering ground for species like the yellow croaker fish and blue crab, among many others, according to environmental group Greenpeace. 

It is also on the migratory pathway of numerous marine mammals, such as humpback and grey whales.