Burnt debris from the wreck of the containership X-Press Pearl is now affecting more than 150 km (81 nautical miles) of Sri Lanka's coastline.
That is according to International Tanker Owners' Pollution Federation (ITOPF) experts who are on site.
The Sri Lankan Marine Environmental Protection Authority (MEPA) is working with the Sri Lanka Navy to coordinate the pollution clean-up.
The ITOPF said more than 1,000 people are involved "most days" in the operation. Specialist pollution response company Oil Spill Response has also arrived in Sri Lanka and will work with the ITOPF in providing technical assistance.
The wreck of the 2,743-teu X-Press Pearl (built 2021), which partially sank after a blaze lasting two weeks, is 10 km off the coast near the Sri Lankan city of Negombo, which is around 12 km north of the capital city Colombo. The wreck is aground at a depth of 21 metres.
The MEPA has set up a sampling programme to determine the extent of pollution from the vessel. The ship is reported to have been carrying 46 different chemicals including nitric acid and sodium dioxide.
The clearest evidence of pollution has come from billions of tiny plastic pellets, known as nurdles, which have washed up onto the beach.
“The pollutants of particular concern are nurdles, as they have the potential to spread over vast distances and recovery of these small plastic pellets can be difficult and protracted,” the ITOPF said.
According to a BBC report, the nurdles have also been found in dead fish, which have washed up onto the shore. Dead turtles and dolphins are also reported to have been found.
There are wider concerns about the longer-term impact of pollution from the vessel on the Sri Lanka environment, its coral reefs and fishing industry.
“The fish are bred in the coral reefs in the area and authorities are saying that all those breeding grounds are destroyed due to the dangerous chemicals,” local fisherman Tiuline Fernando told the BBC. “There is no other option than jump into the sea and die.”
The ITOPF said no bunker pollution has been detected so far, although a sheen emitting from the vessel is under investigation. The Sri Lanka Navy has been carrying out underwater inspections to detect any pollution from bunker fuel.
X-Press, the the Singapore-based operator of the vessel, said: “The salvors remain on scene to deal with any possible debris supported by the Sri Lanka Navy and the Indian Coast Guard, who have oil spill response capabilities on standby.”
The prospect of a prolonged impact on the environment could see the eventual insurance bill soar. Marine casualty pollution costs are usually met by protection and indemnity insurers.
The X-Press Pearl's P&I cover is with the London P&I Club, which shares claims of more than $10m with other International Group of P&I Club members.