Reuters: Danish shipping and oil group A.P. Moller-Maersk said on Thursday it was investigating sightings of an oil slick near three of its North Sea fields but that it could not identify any spill. Oil on the surface of the sea was observed by Danish and German reconnaissance aircraft on Tuesday and Wednesday near the Dan, Halfdan and Kraka fields in the North Sea, Maersk Oil said in a statement on Wednesday. An official at the Danish Environmental Protection Agency (EPA) said the …