Smoke billows from the Singapore-registered container ship MV X-Press Pearl, which has been burning for the 11th consecutive day as vessels try to douse off the fire, in the sea off Sri Lanka's Colombo Harbour on Sunday. Photo: AFP

Sri Lankan authorities Sunday said they will sue the owners of a Singapore-registered cargo carrier which has burned for 11 straight days off the island's west coast and caused some of its worst-ever marine pollution.

Police said a criminal investigation was also launched into the blaze aboard the MV X-Press Pearl, which was carrying 25 tons of nitric acid and a huge amount of plastic raw materials.

The intense fire, still burning at the rear of the 186-meter vessel, has destroyed much of the cargo, some of which also fell into the Indian Ocean.

Tons of microplastic granules have inundated the South Asian nation's famed beaches, forcing a fishing ban and sparking fears of ecological devastation.

Sri Lanka's Marine Environment Protection Authority said it met with attorney general Sanjaya Rajaratnam on Sunday to plan legal action against the owners of the vessel, its crew, as well as insurers.

"We have gone through the details and will be taking action against those responsible," MEPA Chairman Dharshani Lahandapura told reporters in Colombo.

She said they were, however, yet to make an assessment of the environmental damage, but she believed it was the "worst marine pollution" Sri Lanka has ever suffered.

Sri Lanka's navy chief, Vice Admiral Nishantha Ulugetenne, who was also at Sunday's talks with the island's chief prosecutor, said the X-Press Pearl was still on fire, but the blaze was now under control.

But he ruled out towing it away from Sri Lankan waters until the fire was completely put out and experts examined the vessel for any structural weaknesses.

AFP