The reefer Silver Bergen´s peculiar trail in Øresund

Tonight the Norwegian reefer Silver Bergen left a rather peculiar "trail" when it passed Hittarp in the Sound. It appeared that the ship had emptied something hot into the sea, because the "smoke" you see on the picture did not come from the funnel. The question is, what was it?

The "trail" after Norwegian reefer Silver Bergen at 6.31 PM this evening. 

The Silver Bergen half a minute later.