As of Thursday, 130 marine animals have been found dead on the Indian Ocean's beaches since the MV X-Press caught fire last month before partially sinking off the coast after two weeks ablaze.
Sri Lanka's government believes they were killed by the hundreds of tonnes of chemicals and plastics leaking from the ship.
"At least six turtle carcasses washed up along the western coast on Thursday alone," a wildlife official told AFP.
He said they had also received the first report of a shoal of reef fish dying at Hikkaduwa, a southern tourist resort area known for its rich coral reefs.
"So far we have collected the carcasses of 115 turtles, 15 dolphins and five whales," the official said, asking not to be named.
They include a blue whale carcass found off the northern Jaffna peninsula, about 400 kilometres (250 miles) north of Colombo, last week.
Officials are awaiting the results of forensic reports, he said.
The Singapore-registered ship was known to be carrying 81 containers of hazardous chemicals, including 25 tonnes of nitric acid, when it caught fire.
Around 1,200 tonnes of tiny plastic pellets and other debris that blanketed beaches have been scooped up and are being stored in 45 shipping containers.
Sri Lanka is seeking $40 million in damages from the ship's operators X-Press Feeders.
Local police have launched a criminal probe against the ship's captain, chief engineer, chief officer as well as its local agent.
Environmentalists are also suing the government and the owners for allegedly failing to prevent the disaster.
The Sri Lankan navy said meanwhile Friday that another container ship on its way from Colombo to Singapore had reported an engine room fire and that one crew member was missing.
Around 200 container ships and oil tankers sail past Sri Lanka every day on the busy routes between Asia, the Middle East and Europe. Many dock in Colombo, the biggest transhipment hub in South Asia.
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