COLOMBO: A burnt-out container ship that has already caused Sri Lanka’s worst maritime environmental disaster was sinking Wednesday with several hundred tonnes of oil still in its fuel tanks, the navy said.

The MV X-Press Pearl, carrying hundreds of tonnes of chemicals and plastics, burned for 13 days within sight of the island’s coast before rescue workers finally managed to extinguish the blaze on Tuesday.

A huge amount of plastic debris has already inundated beaches, and authorities now fear an even greater disaster should the 278 tonnes of bunker oil and 50 tonnes of gas in the Singapore-registered ship’s fuel tanks leak into the Indian Ocean.

As tugs on Wednesday began trying to tow the ship further out to sea, navy spokesperson Indika de Silva said it was slowly sinking.

“The stern of the ship is under water, the water level is above the deck,” de Silva said.

“The ship is going down.”

Some oil was already visible near the beaches of Negombo, about 40 kilometres (25 miles) from Colombo, an AFP photographer said, although it was not clear if it was from the stricken ship.

De Silva said the navy helped Dutch salvage firm SMIT to board the vessel and establish a tow connection after several attempts overnight failed due to bad weather.

“The ship will be towed as further away from the coast as possible before it goes down completely,” he added.

Fisheries minister Kanchana Wijesekera tweeted that the salvage company involved in the operation “has indicated that the vessel is sinking at the current location”. An official involved in the mitigation efforts said earlier that local experts feared the vessel was unstable. “The fire-fighting efforts also saw a lot of water sprayed onto the decks. Much of that water has settled in the stern,” the official told AFP.