A black box from a ship loaded with chemical and plastic that is sinking off Sri Lanka has been located, officials said Sunday, as investigators probe what caused the vessel to catch fire.

The Singapore-registered container ship MV X-Press Pearl carrying hundreds of tonnes of chemicals and plastics has been slowly sinking after a fire
The Singapore-registered container ship MV X-Press Pearl carrying hundreds of tonnes of chemicals and plastics has been slowly sinking after a fire AFP / ISHARA S. KODIKARA

The Voyage Data Recorder, also known as a maritime "black box", enables investigators to review procedures and instructions ahead of an accident.

Sri Lankan authorities said they hope it will provide details of the ship's movements and its communications with the harbour in the capital Colombo, where it had been due to dock.

Tonnes of microplastic granules from the ship have swamped an 80-kilometre (50-mile) stretch of beach in Sri Lanka
Tonnes of microplastic granules from the ship have swamped an 80-kilometre (50-mile) stretch of beach in Sri Lanka AFP / LAKRUWAN WANNIARACHCHI

"The navy facilitated technicians to remove the VDR from the bridge which is still above the waterline," navy spokesman Indika de Silva told AFP.

The Singapore-registered MV X-Press Pearl has been slowly sinking into the Indian Ocean since Wednesday after a fire that raged for nearly two weeks within sight of the coast.

Map locating the area off Sri Lankan west coast where a burnt-out container ship started sinking on Wednesday.
Map locating the area off Sri Lankan west coast where a burnt-out container ship started sinking on Wednesday. AFP / STAFF

The ship, carrying 25 tonnes of nitric acid and a huge amount of plastic raw materials, was heading to Colombo from Gujarat, India.

Sri Lankan officials have said an acid leak since May 11 may have sparked the blaze. Ports in Qatar and India had refused to offload the leaking nitric acid, they added.

Police on the island nation launched a criminal investigation, interviewing the vessel's skipper and chief engineer -- both Russians -- and its chief officer, an Indian, and seizing their passports.

Authorities are bracing for a possible oil spill after the stern submerged. There has been no sign of any leaks so far, they added.

Tonnes of microplastic granules from the ship swamped an 80-kilometre (50-mile) stretch of beach declared off-limits for residents. Fishing in the area was also banned.

Sri Lankan environmentalists on Friday sued the government and the ship's operators for allegedly failing to prevent what they called the "worst marine disaster" in the country's history.