A series of explosions were heard on Friday in the Iranian oil tanker that has been fire since the weekend, said China’s state media Xinhua.

The Sanchi tanker keeps exploding, hampering efforts to extinguish the fire and rescue survivors, it reported citing the Ministry of Transport.

This has increased concerns that the ship may break up and sink.

The week-long rescue effort following the tanker's collision with a freight ship on Saturday night has been roiled by poor weather, including 3-meter (10 feet) high waves and strong winds, and toxic fumes from the burning oil.

Dozens of the rescue boats were forced to retreat from dousing the tanker with foam on Wednesday due to an explosion.

The tanker had drifted into Japan’s exclusive economic zone (EEZ) on Wednesday afternoon, a spokesman for Japan’s Coast Guard told Reuters on Friday, as strong winds pushed the burning ship away from the Chinese coast.

The ship was about 300 km (186 miles) northwest of Sokkozaki on the island of Amami Oshima as of Thursday afternoon, a spokesman from the Coast Guard’s 10th region based in Kagoshima said.

Amami Oshima is one of the northern islands in the Ryukyu islands chain that includes Okinawa.

The tanker Sanchi (IMO:9356608), owned by Iran’s top oil shipping operator National Iranian Tanker Co, was carrying almost 1 million barrels of condensate, an ultra-light, highly flammable crude oil, to South Korea.

It collided with the freighter CF Crystal (IMO:9497050) that was carrying grain from the United States about 160 nautical miles (184 km) off China’s coast near Shanghai.

The spokesman said that Chinese authorities turned down an offer from the Japanese Coast Guard to help, saying it would ask for help when needed.

The Coast Guard has sent patrol boats and aircraft to monitor the situation, he said.

According to China’s state-owned China Central Television(CCTV), the tanker drifted about 25 miles (40 kms) to the south over the past two days, as of 9 a.m (0100 GMT) on Friday.

About 14 rescue vessels are attempting to put out the fire and searching for missing crew members from the tanker, CCTV reported citing Shanghai Maritime Search and Rescue Centre.

The Sanchi had a crew of 32 sailors at the time of the collision. The body of a mariner suspected to be from the ship was recovered on Monday and sent to Shanghai for identification. The rest of the crew, which included 30 Iranians and two Bangladeshis, remains missing.