Rescue crews have wrestled to bring a blaze on an Iranian oil tanker off China’s east coast under control as fire rages for a second day following a collision with a grain ship.

Concerns were growing that the tanker, which hit a freight ship on Saturday night in the East China Sea and burst into flames, may explode and sink, the official China Central Television (CCTV) said on Monday, citing experts on the rescue team.

Poor weather continued to hamper the rescue work, Lu Kang, a spokesman at China’s foreign ministry, told a news briefing.

The extent of the environmental harm and size of the oil spill from the ship were not known, but the disaster has the potential to be the worst since 1991 when 260,000 tonnes of oil leaked off the Angolan coast.

The remains of one of the 32 mariners on board was found on Monday afternoon, Iranian and Chinese officials confirmed.

Mohammad Rastad, head of Iran’s Ports and Maritime Organisation, was quoted by the ISNA news agency as saying that the body had been sent to Shanghai for identification. The fate of the remaining 31 sailors is not known.

The Sanchi tanker run by Iran’s top oil shipping operator, National Iranian Tanker Co, collided with the CF Crystal on Saturday evening about 160 nautical miles off China’s coast near Shanghai and the mouth of the Yangtze River Delta.

Chinese state media CCTV showed footage of a flotilla of boats dousing the flames with water as plumes of thick dark smoke continued to billow from the tanker.

One portion appeared to show the fire had been extinguished, although this could not be independently confirmed. China’s Ministry of Transport and Maritime Safety would not comment when asked if the fire was out.

China sent four rescue ships and three cleaning boats to the site, South Korea dispatched a ship and a helicopter, while a US Navy military aircraft searched an area of about 3,600 square nautical miles for crew members.

The Panama-registered tanker was sailing from Iran to South Korea, carrying 136,000 tonnes of condensate, an ultra-light and highly volatile crude. That is equivalent to just under one million barrels, worth about $US60 million ($84 million), based on global crude oil prices.