The DNR is investigating a major fish kill in the Rock River at Waupun. Waupun Deputy police chief Jeremy Rasch says hundreds of dead fish were found in the river near the Mill Pond. Rasch says a DNR biologist believes some type of chemical from run-off following heavy rain last week impacted oxygen levels in the river. Rasch says hundreds of fish including bass, carp and crappie were found floating in the river. Tests taken this week show oxygen levels in the river are back to normal.