Officials say the northwest Iowa city of Cherokee accidentally released several hundred gallons of wastewater.
The state Department of Natural Resources says the release happened Thursday after a relief valve failed on a force main.
Officials say the untreated water entered a storm sewer that flows into the Little Sioux River. Most of the wastewater soaked into the ground.
Repairs were completed about 2 p.m. Thursday. DNR officials will continue to monitor the incident.