Despite much rescue efforts, the oil tanker is on fire and is feared to be on the verge of explosion.
The tanker owner said it was hopeful that some or all of the crew members were in a safe part of the vessel and would be rescued. The two other crew members are from Bangladesh.
Cleanup and rescue ships have faced toxic fumes, rain and windy conditions as they scrambled to find survivors and avoid a massive oil slick since Saturday's incident.
The tanker Sanchi, run by Iran's top oil shipping operator, National Iranian Tanker Co, collided on Saturday with the CF Crystal, carrying grain from the United States, about 300 kilometres off China's coast near Shanghai.
South Korean authorities have said that the flames could last for up to a month given the consequences of previous oil spills.
The collision has also raised fears of oil contamination, although Chinese authorities have said claimed that this is unlikely due to the lightness of condensate, causing it to evaporate quickly.
A simulation test also found that less than one percent of oil content would remain on the sea surface five hours after a condensate oil leak. A flotilla of 13 search-and-rescue vessels is still looking for them in the 900-square-nautical-mile area around the oil tanker.
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The body recovered had yet to be identified but was wearing a protective suit created to withstand cold seawater.
The blaze, started by a collision with a freight ship, was raging for a fourth day on Wednesday. Rescuers on Tuesday found a body believed to be a crewmember from the Iranian-operated tanker but there has been no sign of survivors.
"There is a good possibility that people are still alive", he added, while indicating that he had no solid information.
An Iranian crude oil tanker, Sanchi, collided with Chinese freighter CF Crystal during the weekend.
The 21 Chinese crew member of the Crystal, which did not burst into flames, were all rescued.
Park Sung-dong, an official from South Korea's ministry of oceans and fisheries, said: "We can't grasp the level of oil contamination at this moment". The ship and its cargo were insured.
The tanker had been sailing to Daesan in South Korea from Kharg Island in Iran, according to Reuters ship tracking data.