The size of the spill is still unclear. The fog is causing problems for the Swedish Sea Rescue Society, which is working at the site:

"It doesn't look so good because we can't see much. Visibility is terrible, but we've had a lot of boats out driving around – and it's thick with oil. Especially a bit north of Hörvik where we are now, says Anton Kock, sea rescuer at the Swedish Sea Rescue Society.

Now the Sea Rescue Society, together with the Coast Guard and the Rescue Service, will lay out the bilge.

"It's to protect the land and islands and bays," says Anton Kock.

The ferry Marco Polo was on its way from Trelleborg to Karlshamn. On board were 41 passengers and 29 crew members, no one was injured when the ship ran aground.