The United Nations representative in Sri Lanka has said the sinking of a container ship that caught fire while transporting chemicals off the coast of the capital has caused “significant damage to the planet” by releasing hazardous substances into the ecosystem.

The Singapore-flagged MV X-Press Pearl sank off Colombo on Thursday a month after catching fire, raising concerns about a possible environmental disaster.

The UN said it was coordinating international efforts and helping Sri Lanka in assessing the damage, recovery efforts and preventing such disasters in the future.

“An environmental emergency of this nature causes significant damage to the planet by the release of hazardous substances into the ecosystem,” UN Resident Coordinator in Sri Lanka Hanaa Singer-Hamdy said in a statement late on Saturday. “This, in turn, threatens lives and livelihoods of the population in the coastal areas.”

A UN team of oil spill and chemical experts – provided by the European Union – has been sent to Sri Lanka.

Sri Lanka has already submitted an interim claim of $40m to X-Press Feeders – the ship’s operating company – to cover part of the cost of fighting the fire, which broke out on May 20 when the vessel was anchored about 9.5 nautical miles (18 kilometres) northwest of Colombo and waiting to enter the port.

Environmentalists are suing the government and X-Press Feeders for allegedly failing to prevent Sri Lanka’s worst marine environmental disaster, while Sri Lankan police have launched a criminal investigation into the incident.

Last week, experts recovered the data recorder from the fire-stricken vessel.

The Sri Lankan navy believes the blaze was caused by its chemical cargo, which included more than 22 tonnes of nitric acid and other chemicals, most of which were destroyed in the fire. But debris including burned fibreglass and tonnes of plastic pellets have already polluted nearby beaches.

Tonnes of microplastic granules have inundated the South Asian country’s famed beaches in Negombo, a popular tourist destination, forcing a fishing ban and prompting fears of ecological damage.

Local media reports have said more than 50 turtles and eight dolphins have been found dead across the island since the ship caught fire on May 20. The country’s top environment official, Anil Jasinghe, on Thursday linked the deaths to the X-Press Pearl, but said he was still waiting for final autopsy reports.

A ship manifest seen by The Associated Press said the ship was carrying just under 1,500 containers, with 81 of those described as “dangerous” goods.

The main concern has been about 300 tonnes of bunker oil used as fuel for the ship. But officials have been saying it could have burned off in the fire.

Both Sri Lankan authorities and the ship’s operator have said so far there is no sign of an oil spill.

The Sri Lankan navy believes the blaze was caused by its chemical cargo, which included more than 22 tonnes of nitric acid and other chemicals [File: Sri Lanka Navy/AP]