There are fears of an environmental disaster in the East China Sea as a tanker continues to leak oil two days after colliding with a cargo ship.

Chinese officials have told state media the vessel is in danger of exploding and sinking.

Rescuers attempting to reach the site were being beaten back by toxic clouds, the transportation ministry has said.

The crew, 30 Iranians and two Bangladeshis, remain missing despite international rescue efforts.

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The extent of the spill and environmental hazard are still unclear. The vessel was still ablaze on Monday morning.

The tanker had been carrying an ultra-light form of oil known as condensate which in the case of a spill can be more dangerous for the environment than regular crude.

“Condensate is more likely to evaporate and mix in with the water,” John Driscoll of JTD Energy Services told the BBC.

“It also can be colour- and odourless – so it is a lot harder to detect, contain and clean up.”

Though Panama-registered, the tanker Sanchi belongs to an Iranian company.

The Sanchi was carrying 136,000 tonnes of Iranian oil when the vessel collided with a Chinese cargo ship on Saturday night, 165 nautical miles east of Shanghai.

The 21-strong crew of the Chinese ship were rescued.

China has sent several ships to carry out search-and-rescue operations while South Korea helped with a coast guard ship and a helicopter.

The US Navy had also sent a military aircraft to help with the rescue efforts.