The Department of Natural Resources says it's investigating a large manure spill in St. Croix County that happened in December but wasn't reported until March 29. The DNR reported Wednesday the spill occurred at the Emerald Sky Dairy in the Town of Emerald, which is currently permitted to have around 1,700 cows. A statement from DNR Spokesman Andrew Savagian said the agency is still investigating. Emerald Sky Dairy has been seeking a permit to expand its operations since March of 2016. The plan is to grow the dairy to 5,860 milking cows and 3,000 calves. The DNR is reviewing the permit application.