The Sanchi had on board 136,000 tonnes of condensate, which is an ultra-light version of crude oil.
The Panama-flagged vessel was bringing the condensate from Iran to South Korea when the collision with the Hong Kong-registered freighter CF Crystal, carrying grain from the US, happened in the East China Sea. The crewmen of the Crystal were all rescued.
The cause of the collision is still not known.
Condensate is very different from the black crude that is often seen in oil spills.
It is toxic, low in density and considerably more explosive than regular crude.
Condensate creates products such as jet fuel, petrol, diesel and heating fuel.