BEIJING – Chinese authorities battling to prevent an environmental disaster after a collision between an Iranian tanker and a cargo ship said on Wednesday no major oil spill has been detected, but 31 sailors remained missing.

Cleanup and rescue ships have faced toxic fumes, rain and windy conditions as they scrambled to find survivors and avoid a massive oil slick since Saturday’s incident.

The Sanchi, carrying 136,000 tonnes of light crude oil, has been in flames since colliding with the CF Crystal, a Hong Kong-registered bulk freighter, 160 nautical miles east of Shanghai.

Experts had warned that a spill of the Panamanian-flagged 274-metre (899-foot) tanker’s cargo could spell environmental catastrophe as authorities said the ship could explode or sink.

But China’s transport ministry said in a statement that as of 6:00pm Tuesday, "no large-scale oil spills were found on the sea surface" where the search is being conducted around the stricken vessel, which continued to burn.

The oil from the tanker is condensate oil that is expected to quickly evaporate upon hitting the water, with "very little residue on the water’s surface", the ministry said.

A simulation test also found that less than one percent of oil content would remain on the sea surface five hours after a condensate oil leak.

Thirteen search-and-rescue vessels are continuing to look for missing crew members within 900 square nautical miles of the tanker, the ministry said.

But weather conditions are unfavourable, with "overcast and rainy weather", strong winds and waves.

Of the 30 Iranians and two Bangladeshis on the Sanchi’s crew, only one body has so far been found.

The oil tanker was on its way to South Korea when it collided with the CF Crystal, which was transporting grain to mainland China. The Crystal’s 21 Chinese crew members were all rescued.

The Sanchi belongs to the National Iranian Tanker Company (NITC), Iran’s petroleum ministry said, and was transporting the oil to South Korea’s Hanwha Total. The ship and its cargo were insured, a statement said.

This is the second accident in less than two years involving a tanker owned by the NITC.

In August 2016, an Iranian supertanker and a container ship collided in the Singapore Strait, causing damage to both vessels but no injuries or pollution. – AFP