Tanker Sanchi, run by oil shipping operator National Iranian Tanker Co, collided with a CF Crystal carrying grain from the United States about 160 nautical miles off China's coast near Shanghai on Saturday night.
The P&I reinsurance coverage has still yet to recover entirely to full pre-sanction levels, as the IG member clubs had been banned from providing insurance to Specially Designated Nationals under U.S. sanctions, according to one source with direct knowledge of the matter.
Al Jazeera's Adrian Brown reports from Eastern China.
China's transport ministry said Thursday evening the Panamanian-flagged 274-meter (899-foot) tanker remained on fire, adding two ships had spent the day spraying the vessel with retardant foam.
It wasn't immediately clear what caused the collision, which happened in open seas rather than a narrow channel where such accidents are more common.
An oil slick has spread out from the Iranian tanker at a radius of at least a half-mile.
The Sanchi was carrying 136,000 metric tons (150,000 tons, or almost 1 million barrels) of condensate, a type of ultra-light oil, according to Chinese authorities.
Rescue crews were forced to retreat on Wednesday after a blast on the ship.
By comparison, the Exxon Valdez was carrying 1.26 million barrels of crude oil when it spilled 260,000 barrels into Prince William Sound off Alaska in 1989.
"Probably the Iranian crew has been stationed in the bottom compartments of the ship which are cooler", he was quoted by the official Islamic Republic of Iran news agency as saying before the explosion.
The National Iranian Tanker Co., which carried internationally-credited insurance, said it had formed an emergency committee to investigate the cause of the incident. The National Iranian Tanker Co. describes itself as operating the largest tanker fleet in the Middle East.
A total of 32 crew members, including 30 Iranians and two Bangladeshis, were on board the oil tanker at the time of the collision. "We can not say all of them have died, because rescue teams are there and providing services".
Hanwa Total is a 50-50 partnership between the Seoul-based Hanwha Group and the French oil giant Total.
It is the second crash by an Iranian oil tanker to take place in 18 months, after an Iranian supertanker crashed with a container ship in the Singapore Strait back in July 2016.
Chinese media has shared footage of oil tanker Sanchi puffing black clouds of smoke as rescue boats try to douse the flames.