The Iowa DNR is investigating a fish kill that began on the North Fork of the Floyd River about seven miles northeast of Sheldon in O’Brien County.
On Sunday, DNR staff found dead fish starting close to the intersection of the North Fork and the Floyd River, and continuing for about four miles downstream in the Floyd.
DNR specialists have not yet identified the pollutant source.
Areas further downstream were low in oxygen and high in ammonia.
Laboratory results will be available next week.
The DNR will continue to investigate to locate the source of the pollutant.