China's Transport Ministry has reported an explosion aboard the Iranian oil tanker that collided with a cargo ship off the Asian country’s coast on Saturday.
The ministry said in a statement that the explosion occurred at around 13:35 Beijing time on Wednesday after rescue crew tried to spray foam to put out the blaze.
According to the statement, the blast forced emergency ships to pull back to a safe distance.
Officials also said firefighting and rescue efforts were all suspended.
Sanchi, the tanker run by Iran’s top oil shipping operator National Iranian Tanker Co., burst into flames on Saturday evening after colliding with CF Crystal, a Hong Kong-registered cargo ship, about 160 nautical miles off China’s coast near Shanghai.
So far, the body of one of the 32 missing crew members -- 30 Iranians and two Bangladeshis -- has been recovered. All 21 Chinese crew members of Crystal were rescued.
Earlier, a spokesman for National Iranian Tanker Co. said there was still hope of finding survivors.
Mohsen Bahrami explained that since the vessel's engine room was not directly affected by the fire and was about 14 meters underwater, there was still the possibility of finding the tanker's crew members alive.
Bahrami also noted that fresh operations to extinguish the flames had started on Wednesday morning, with Chinese ships spraying foam onto the burning tanker. He expressed hope that a heliborne rescue operation would begin as soon as the blaze was controlled.
Experts earlier warned that a spill of the tanker's cargo could spell an environmental catastrophe.
However, China's Transport Ministry said in a statement on Wednesday that as of 6:00 p.m. Tuesday, "No large-scale oil spills were found on the sea surface" where the search is being conducted around the stricken tanker.
The statement said the tanker’s cargo is condensate oil that evaporates quickly upon hitting the water and would leave "very little residue on the water's surface" -- less than one percent -- within five hours after a leak.
Meanwhile, South Korea's Ministry of Oceans and Fisheries said on Wednesday that the stricken tanker, which had been carrying 136,000 tonnes of condensate to the Asian country, could burn for as long as one month.
"We believe flames would last for two weeks or a month considering previous cases of oil tank accidents," Park Sung-dong, an official at the ministry, said.
Last year, another oil tanker owned by the National Iranian Tanker Co. collided with a Swiss container ship in the Singapore Strait, damaging both ships, but causing no injuries or oil spill.