The ferry, which is a train ferry, was scheduled to travel from the port of Rostock to Trelleborg when a leak occurred on Wednesday afternoon. It came from a train on the cargo deck, according to Johan Live at Stena Line's press service.
It is a leak of a liquid that is classified as dangerous goods. Rescue services are on site to deal with this, Johan Live tells the newspaper.
Four crew members were exposed to the liquid and have been taken to hospital for examination.
Just over 200 people were on board the ferry.
