An Iranian oil tanker collided with a bulk freighter and caught fire off China's eastern coast, leaving its entire crew of 32 missing and causing the tanker to spill oil into the sea, authorities said Sunday.

The missing - 30 Iranians and two Bangladeshis - are all from the tanker Sanchi, which was floating while still burning early Sunday, said Chinese maritime authorities, who dispatched police vessels and three cleaning ships to the scene.

The South Korean coast guard also sent a ship and an airplane to aid the search effort.

Chinese state media carried pictures of the tanker on fire with smoke plumes daytime Sunday.

The Panama-registered tanker was sailing from Iran to South Korea late Saturday when it collided with the Hong Kong-registered freighter CF Crystal in the East China Sea, 257 kilometers (160 miles) off the coast of Shanghai, China's Ministry of Transport said.

All 21 crew members of the Crystal, which was carrying grain from the United States, were rescued, the ministry said. The Crystal's crew members were all Chinese nationals.

It wasn't immediately clear what caused the collision.

The size of the oil slick caused by the accident was also not immediately known. It was not clear as of Sunday afternoon whether the tanker was still spilling oil.

The Sanchi was carrying 136,000 metric tons (150,000 tons, or nearly 1 million barrels) of condensate, a type of ultra-light oil, according to Chinese authorities. (AP)