Bad weather is hampering efforts to contain a fire and an oil spill – more than 60 hours after two ships collided in the East China Sea, officials say.
China says an Iranian-owned oil tanker is still burning after the incident with a cargo ship about 260km (160 miles) off the coast of Shanghai.
The Sanchi tanker has on board 136,000 tonnes of condensate, which is an ultra-light version of crude oil.
Rescuers have now widened their search for 31 missing crew members.
The body of only one crewman, among the 30 Iranians and two Bangladeshis on board, has so far been found.
Twenty-one Chinese nationals on the cargo ship have been rescued.
There fears of a major environmental disaster as the tanker is continuing to leak oil.
What are the latest developments?
In a statement on Tuesday, the Chinese transport ministry said heavy winds, rain and waves up to four meters continued to hamper efforts to contain the fire.
It said the search and rescue operation was now covering an area of 900 square miles.
A formal accident investigation, involving several government departments, would start on Tuesday, officials said.
Where, how and when did the accident happen?
The Panama-flagged Sanchi was bringing 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 collision, in the mouth of the Yangtze River Delta, occurred on Saturday evening.
The exact cause is not yet known.
What is the Sanchi carrying?
The tanker, run by Iran's leading oil shipping operator, has on board 136,000 tonnes of condensate.
That is about one million barrels and at current prices is worth roughly $60m (£44m).
The Sanchi will also be carrying a certain amount of heavy – and toxic – shipping fuel.
Condensate is very different from the black crude that is often seen in oil spills.
It exists in gas form within high-pressure oil reservoirs and liquefies once extracted.
It is toxic, low in density and considerably more explosive than regular crude oil.
Condensate, which does not need the heavy refining process of denser crude, creates products such as jet fuel, petrol, diesel and heating fuel.
How does this compare with other oil spills?
It is impossible to say at this point because it is unknown how much oil has been, or will be, spilled.
The Sanchi's one million barrels is about 35 million gallons. Even if all of it spilled, it would be less than the major ship disasters listed below, but more than three times the Exxon Valdez spill in 1989, which is considered one of the world's worst environmental disasters.
So, how much the spill affects the environment depends on the location where it occurred. The Atlantic Empress incident listed below – the record spill from ships – saw little oil reach coastlines.
There are also a lot of different types of spill. Arguably the worst was the deliberate release of up to 500 million gallons by the Iraqis in January 1991 during the Gulf War. The resultant slick covered some 10,300 sq km (4,000 sq miles).
As far as ships are concerned:
- The Atlantic Empress and Aegean Captain collided off Trinidad and Tobago in 1979. The Atlantic Empress exploded and 26 crew members died. The 90 million gallon oil spill is a record from ships
- The ABT Summer exploded off Angola in 1991, spilling about 80 million gallons over 200 sq km
- The Castillo de Bellver caught fire and broke apart off Cape Town, spilling 78 million gallons
- The Amoco Cadiz spilled almost 69 million gallons after running aground off Brittany in France in 1978
- The Torrey Canyon hit a reef off Cornwall, England, in 1967, spilling 36 million gallons of crude and affecting almost 200 miles of coastline
- The Exxon Valdez only spilled 11 million gallons in Prince William Sound, Alaska, in 1989 but was a major environmental disaster