The spill, believed to contain up large amounts of heavy fuel oil, was quickly contained in a limited area by oil booms, environmental officials said.

The slick was first spotted near the port of Inkoo, but on Friday the police were still investigating what had caused the spill, Finnish press reported.

The oil spill has also soiled a number of sea birds, and the whole clean-up operation will likely take days, officials said.

The archipelago of Inkoo, some 60 kilometers (35 miles) west of Helsinki, is a popular weekend and holiday destination for people living in the Finnish capital.

TERRA.WIRE