An Iranian oil tanker that's burning out of control off the coast of China reportedly may explode and sink, even as authorities work to recover 31 missing crew members.

At least one crew member has been reported dead on the burning vessel, and there are concerns there may be an explosion, state broadcaster China Central Television reported Monday.

The Sanchi tanker run by Iran’s top oil shipping operator, National Iranian Tanker Co, had been sailing from Iran to South Korea when it collided with the Hong Kong-registered freighter CF Crystal late Saturday in the East China Sea, about 160 miles off the coast of Shanghai, China's Ministry of Transport said.

The remains of one of the 32 mariners on board was discovered on the blazing wreck Monday afternoon, Iranian and Chinese officials confirmed to Reuters.

Mohammad Rastad, head of Iran’s Ports and Maritime Organization, told the ISNA news agency the body had been sent to Shanghai for identification. The fate of the remaining 31 sailors is not known.

Search and cleanup efforts have been hampered by fierce fires and poisonous gases that have engulfed the tanker and surrounding waters, state broadcaster CCTV reported. The South Korean coast guard said Monday that thick smoke is still billowing from a burning oil tanker in the East China Sea and bad weather is also worsening visibility.

China, South Korea and the U.S. have sent ships and planes to the area to search for the Sanchi's crew. The U.S. Navy sent a P-8A aircraft from Okinawa, Japan, to aid the search.

"The Chinese government takes maritime accidents like this very seriously, and has already dispatched many search and rescue teams to the scene to carry out search and rescue,” Lu Kang, a spokesman at China’s foreign ministry, told reporters at a news briefing.

It wasn't immediately clear what caused the initial collision, but all 21 crew members of the Crystal, which was carrying grain from the U.S. to China, were rescued, the Chinese ministry said. The Crystal's crew members were all Chinese nationals.

Kwon Yong-deok, a Korea Coast Guard official, told the Associated Press thick black smoke was still billowing from the ship on Monday afternoon and bad weather was worsening visibility at the scene. The Sanchi was carrying 150,000 tons, or nearly 1 million barrels of condensate, a type of ultra-light oil, according to Chinese authorities, who have dispatched three ships to clean the spill.

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, badly damaging local ecology and the area's fishing-based economy.

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The size of the oil slick from the Sanchi — and the scale of the environmental toll — may be smaller. Unlike the thick crude that gushed out of the Valdez, much of the light, gassy condensate from the Sanchi may have evaporated or burned immediately, Kwon said.

The Sanchi's own fuel that leaked during the collision will be more difficult to clean, officials said.

South Korean petrochemical company Hanwha Total Co., a 50-50 partnership between the Seoul-based Hanwha Group and French oil giant Total, said in an email to the AP it had contracted the Sanchi to import Iranian condensate to South Korea.

A Hanwha Total spokesman, who asked not to be named citing office policies, said there is "little possibility" that condensate would leave traces in the ocean after it burned. He added the losses would be covered by an insurance company. The Sanchi's cargo was estimated to be worth more than $60 million.

The Associated Press contributed to this report.