VILLISCA, Iowa (AP) — An unknown amount of ammonia has entered a small unnamed tributary of the West Nodaway River in southwest Iowa. The state Department of Natural Resources says the anhydrous ammonia was released from the United Farmers Mercantile Co-op in Villisca between Tuesday afternoon and Wednesday morning. It went into a city storm sewer before entering the tributary.

DNR officials detected high concentrations of ammonia throughout the tributary to the river, but no fish kill has been reported. Co-op employees are pumping contaminated water out of the tributary. They are also pumping contaminated water from an on-site pit.

The case remains under investigation.