Explosions rocked a stricken Iranian oil tanker in the East China Sea on Wednesday, forcing maritime authorities to suspend firefighting and rescue efforts as a blaze raged on the vessel for the fourth day after a collision with a freight ship.

The explosion on the Sanchi's bow was the latest setback in the multinational effort to extinguish the blaze and forced rescue vessels to move to a safe distance, China's Ministry of Transport said. It was not immediately known if the explosion was large enough to cause the ship to sink.

Earlier in the day, an official with South Korea’s Ministry of Oceans and Fisheries told Reuters the oil tanker could burn for as long as a month.

Smoke is seen from the Sanchi tanker on Jan. 9, 2018 after it collided with a Chinese freight ship in the East China Sea. (China's Ministry of Transport)

“We believe flames would last for two weeks or a month considering previous cases of oil tank accidents,” Park Sung-Dong said.

The Sanchi was carrying nearly 1 million barrels of ultra-light oil when it collided Saturday evening with a freighter 160 miles off the coast and caught fire. The cause of the collision remains unclear.

IRANIAN OIL TANKER BURNING FOR THIRD DAY, MAY EXPLODE AS CREW STILL MISSING

Intense flames, bad weather and poor visibility have hampered rescue efforts in the following days. Rescues have also faced the threat of poisonous fumes from the hulking wreck.

Rescuers on Tuesday found a body believed to be a sailor from the Iranian-operated tanker, while a search continued for 31 other missing crew members.The Iranian company who owns the ship said there is still hope of finding survivors.

The Panama-registered tanker "Sanchi" is seen ablaze after a collision with a Hong Kong-registered freighter (CCTV via AP)

A spokesman for National Iranian Tanker Co. told The Associated Press in Tehran rescuers "likely" will find survivors.

IRANIAN OIL TANKER BURNING OFF CHINA MAY EXPLODE, BODY FOUND IN SEARCH FOR MISSING CREW

"Since the vessel's engine room is not directly affected by the fire and is about [46 feet] under water, there is still hope," spokesman Mohsen Bahrami said late Tuesday. "We are persistently working to put out the fire and rescue possible survivors."

Mahmoud Abuli Ghasemabadi, the brother of missing Iranian sailor Ehasan Abuli Ghasemabadi, told the AP he and other families remained hopeful for good news.

The Panama-registered tanker "Sanchi" caught fire after a collision off the coast of China. (Korea Coast Guard)

"I ask countries that are in that region and can offer any assistance to help us deal with this situation as soon as possible," Ghasemabadi said.

It's the second collision for a ship from the National Iranian Tanker Co. in less than a year and a half. In August 2016, one of its tankers collided with a Swiss container ship in the Singapore Strait, damaging both ships but causing no injuries or oil spill.

The Associated Press contributed to this report.