Nine Chinese crew members are missing after a Taiwanese tanker carrying 58,000 tonnes of naphtha, a highly flammable liquid, collided with a cargo ship in one of the world's busiest shipping lanes.
A fire broke out on the tanker, en route from the United Arab Emirates to South Korea, after the collision at 10pm (14:00 GMT) in the Strait of Malacca, between Malaysia and Indonesia, on Tuesday, maritime police said.
Firefighters were fighting the blaze on the MT Formosa Product Brick, although there was said to be no danger of oil spill from the tanker and the movements of other ships have not been affected.
"The MT Formosa Product Brick is on fire and is now listing on its left side. We fear it may sink," Rizal Ramli, a local marine police chief, said.
"The collision happened last night in clear weather off Port Dickson. We have rescued 16 crew members, mainly of Chinese nationality," he said.
Ramli said two of the rescued crew were Taiwanese.
Captain Ahmed Bin Othman, the director-general of Malaysia's marine department, told Al Jazeera that attempts to search for the missing crew were continuing both in the water and on the tanker, but that the heat of the fire was too intense for rescue workers to board the ship.
"The vessel has drifted outside the traffic separation scheme and currently it remains outside the traffic seperation scheme," he said.
"The tanker was south bound, heading for [South] Korea and the bulk carrier had just left Port Dickson. It was joining the traffic separation scheme and unfortunately they collided in the middle."
Port Dickson is in Negeri Sembilan, south of Kuala Lumpur, the Malaysian capital.
Othman said that the masters of both vessels were being interviewed to ascertain the cause of events.
Accidents in the narrow Strait of Malacca, through which at least 94,000 ships sail annually, are rare.
The waterway is one of the busiest in the world and is crucial to Japan's national interests as more than 80 per cent of its oil is carried through it.