Manure runoff has affected miles of waterways in Fond du Lac County, according to the Wisconsin Department of Natural Resources.
The manure's reached the Sheboygan River at CCC Highway, near the Malone and Mt. Calvary areas, according to the DNR.
A dairy farm put manure on fields starting Friday, and after heavy rain the manure washed into nearby waters, according to the DNR.
Approximately 11 1/2 miles of streams have been affected and the clean-up could continue for days, according to the DNR.
Officials warned people not to get into the water or come into contact with it, but don't expect impacts on wells, with clay soil helping to protect groundwater.