The Swedish Coast Guard has discovered large quantities of a substance in the Baltic Sea that could be biofuel. The carpet was first discovered in the Bothnian Sea between Sweden and Finland and now stretches over 77 square kilometers, the Coast Guard said on Thursday.

Photos showed a long carpet with the substance on the open sea. According to the Coast Guard, it extended into both the Swedish and Finnish economic zones. According to the information, it is not yet clear what exactly the substance is. However, it is not mineral oil and there is currently no risk that the substance could reach the coast.

According to the coast guard, they got an overview of the extent of the pollution from an airplane and took samples. The examination of the samples should last until next week, before that no more precise information is possible. The Coast Guard also checked which ships were in the area and what cargo they had on board.