COLOMBO — Sri Lanka announced an investigation Thursday (June 10) into a possible oil slick reported off its west coast where a container ship is submerged after burning for 13 days.

Coast conservation minister Nalaka Godahewa said local experts were asked to examine an oil patch of about 0.35 square kilometres (0.13 square miles) where MV X-Press Pearl ran aground earlier this month.

"I visited the area by boat yesterday and what we noticed was a thin film of oil which looked like diesel," Dr Godahewa told reporters in Colombo. "It did not look like bunker oil, but we have asked our experts to examine."

The X-Press Pearl reported an onboard acid leak and caught fire just as it was due to enter the Colombo harbour on May 20.

The fire was put out after 13 days, but the vessel's stern hit the bottom of the shallow sea when a tug attempted to move it to deeper waters.

Authorities are bracing for a possible oil spill from the submerged wreck or almost 300 tonnes of bunker oil thought to be still in its fuel tanks.

The owners of the vessel have already deployed representatives from the International Tankers Owners Pollution Federation (ITOPF) and Oil Spill Response (OSR) to monitor any oil spill and help with the clean up of beaches.

Dr Godahewa said five vessels, including two Indian Coast Guard ships equipped to deal with oil spills, were anchored around the sinking vessel, but none reported a leakage from the submerged wreck.

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 has been banned.

Sri Lankan environmentalists last week 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. AFP