Swedish coast guard officials said the slick comprised an estimated 3.5 tons of heavy fuel oil. It had a brown appearance and was described as toxic.

Sweden dispatched a clean-up vessel to the island, off the south-eastern extremity of the country. The weather made it unlikely for the time being that the slick would reach shore, the officials added.

The Fu Shan Hai, a bulk carrier, sank in the waters between Sweden and Denmark on May 31 after colliding with a Polish freighter, causing a major oil spill in the area. It was carrying 66,000 tons of fertilizer and 1,700 tons of bunker fuel.

A fresh spill was caused last week by the failure of a pump being used to empty remaining fuel from the vessel. More than 1,300 tons of oil washed onto Swedish beaches and was being cleaned by hundreds of volunteers.

Oil pollution of the Baltic Sea is of particular concern to environmentalists because of the slow rate of natural cleansing. The sea has only a narrow outlet to the ocean, and any pollution tends to remain for a long time.

TERRA.WIRE