Media playback is unsupported on your device Media caption Huge plumes of smoke were seen rising from the tanker

No large oil spill has been detected so far from a tanker that has been burning since Saturday evening off the coast of China, Chinese officials say.

The Sanchi is still alight and bad weather - with waves of up to 4m (13ft) - is hampering the rescue work.

The vessel collided with a cargo ship about 260km (160 miles) off the coast of Shanghai.

Of the 30 Iranians and two Bangladeshis on the tanker, only one body has so far been found.

Twenty-one Chinese nationals on the cargo ship were rescued.

The Sanchi tanker has on board 136,000 tonnes of condensate, which is an ultra-light version of crude oil.

What are the latest developments?

China's transport ministry said heavy winds, rain and high waves continued to hamper efforts to contain the fire.

Image copyright AFP/Getty Images Image caption The oil tanker was still burning on Tuesday

However, it added that experts at the scene believed that, given the wave conditions, no more than 1% of the condensate was on the surface of the water.

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 about one million barrels of condensate, which 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?

The harm from oil pollution depends on a number of factors, not just on how much is spilled.

Location is paramount, followed by factors such as the type of oil, sea conditions, wave directions, climate and time of year.

The Atlantic Empress incident listed below - the record spill from ships - saw little oil reach coastlines, whereas the Exxon Valdez, which spilled eight times less, is considered one of the world's worst environmental disasters.

Image copyright AFP Image caption Cleaning up after the Torrey Canyon disaster in 1967

Arguably the worst spill 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: