Tons of charred plastic pellets from a burning container ship washed ashore near Sri Lanka's capital Friday as an international effort to salvage the vessel dragged into a ninth day, AFP reported.

Officials said the vessel was known to carry at least 28 containers of the pellets that are used as a raw material in the packaging industry.

The fire broke out on May 20 as the ship waited to enter the Colombo port.

It is also carrying 25 tons of nitric acid, an unspecified quantity of ethanol and lubricants in its 1,500 containers.

Authorities believe the fire was caused by a nitric acid leak which the crew had been aware of since May 11, Sri Lanka's Marine Environment Protection Authority (MEPA) said.

MEPA chairman Dharshani Lahandapura said the crew could have avoided the disaster had they offloaded the leaking containers or returned them to the port of origin before entering Sri Lankan waters.