An oil tanker has collided with a cargo ship off China's east coast, near Shanghai, leaving thirty-two people missing.
The tanker called Sanchi, carrying 136,000 tonnes of Iranian oil worth $60m, has been burning for nearly 24 hours after catching fire after the crash.
Mohammad Rastad, the head of Iran's Ports and Maritime Organisation, said: "poor weather and plumes of smoke rising from the tanker are making rescue attempts difficult."
China's ministry of transport said the fierce blaze has hampered rescue efforts of the missing crew, 30 Iranians and two Bangladeshis.
The ministry released a statement saying, "Sanchi is floating and burning, there is an oil slick and we are pushing forward with rescue efforts.
"The 21 member crew of the cargo ship have been rescued."
The Hong Kong-registered cargo ship, CF Crystal, was carrying 64,000 tonnes of grain from the US to Guangdong province in southern China. Its rescued crew were all Chinese nationals, the country's transport ministry said.
The tanker was on its way to South Korea when the accident happened on Saturday night, about 160 nautical miles (296 km) off the coast of Shanghai.
Oceanographer, Dr Simon Boxall, told the BBC: "This is a big spill,
"Potentially the entire load, 136,000 tonnes, could end up in the ocean, and that would put this in the top 10 spills of all time, so it is significant.
"The only positive side is that, at the moment, the winds are keeping the oil offshore. The chances of it reaching the shore are fairly slim. But we are looking at a lot of oil here and the water depth in that area is only about 50m to 60m, so in the immediate area it will have a dramatic impact."
China's official Xinhua news agency was quoted as saying that eight Chinese ships have been deployed to carry out the search-and-rescue operation while South Korea has also sent a coastguard ship and a helicopter to aid the relief effort.
According to Reuters ship tracking data, the tanker was carrying a cargo equivalent to slightly under a million barrels was sailing to Daesan in South Korea from Kharg Island in Iran.
Check out the video below for footage of the blaze.