The North Dakota Department of Health is investigating several cases of illegal disposal of under-treated wastewater related to oil activity.
A press release says the investigation is in response to reports coming in from the public.
The health department says it's also working with other state and federal agencies that are addressing illegal wastewater disposal, including the EPA's Criminal Investigation Division.
Illegal disposal of under-treated or untreated waste violates state and federal law and can pose a threat to public and environmental health.
Residents and workers in areas with oil activity are asked to help identify illegal waste disposal that may be happening.
Anyone who suspects or witnesses the potential illegal disposal of waste should contact the local police department, local public health unit or the North Dakota Department of Health.