Part of the stricken NITC tanker Sanchi has exploded off China, according to Chinese authorities cited by CNN.
No further details were available on Wednesday afternoon.
Chinese authorities warned on Monday that the vessel could explode.
The transport ministry reported that 14 vessels were searching for 31 crew before the blast.
Earlier on Wednesday, fears of a catastrophic oil slick appeared to have dissipated, at least for now.
Chinese authorities say that no large oil slick has been detected from the burning tanker. This is due in part to the light and highly volatile nature of its cargo of condensate, which has been burning off or evaporating very quickly.
Experts quoted by Reuters claim that the evaporation rate is sufficiently high enough that within five hours of a spill it would leave a residue of less than one percent.
Korean authorities taking part in the rescue efforts told Reuters today that they were more concerned about a possible bunker fuel spill should the ship sink.
Yesterday NITC managing director Siroos Kianersi told TradeWinds that the possibility of the ship exploding or sinking was low.
Photos of the 164,000-dwt Sanchi (built 2008) released by the ministry and taken yesterday afternoon show that the intensity of the fire had died down, with smoke indicating that it is now largely confined to the midships area of the vessel.
Photos taken earlier in the week appeared far more apocalyptic with the ship blazing from stem to stern.
The fire on the ship could burn for as long as a month, South Korea's ministry of oceans and fisheries told Reuters on Wednesday.
"We believe flames would last for two weeks or a month considering previous cases of oil tank accidents," said official Park Sung-Dong.
Rescue boats were still battling strong winds, high waves and toxic fumes to locate the missing 31 crew.
The body of one deceased crew member was recovered on Monday. Yesterday an NITC official confirmed that the body was that of an Iranian national, but did not release details of his identity.
The Sanchi’s crew comprised of 30 Iranians and two Bangladeshis.
The ship collided with the 76,000-dwt bulker CF Crystal (built 2011) in the East China Sea on Saturday night while it was en route from Iran to South Korea.
