State officials say ammonia used as a refrigerant in a Wells Blue Bunny plant is the likely cause of a fish kill in a small stream near Le Mars.

Julie Sievers of the Iowa Department of Natural Resources says the dead fish were first reported early Thursday morning by a person who’d been on a bike path near the stream.

“We sent one of our environmental specialists to investigate and he determined that there were elevated levels of ammonia in that stream,” Sievers says. “Working with city officials, he traced it back to the cooling water discharge from Wells Blue Bunny north plant.”

Ammonia is not typically part of the water that’s discharged from the plant.

“The cooling used to circulate and used as part of their refrigeration process,” Sievers says, “and that water is discharged to the city’s storm water system and out this ‘outfall’ as part of the process.”

The stream drains into the Floyd River, but investigators say there are “no obvious issues” in the river. Elevated ammonia levels are toxic for fish and several hundred dead minnows and chubs were found in the unnamed creek. Sievers says officials from Wells Blue Bunny are investigating to find out where the ammonia may have come from.

“Ammonia is used as the refrigerant and that’s very typical in industrial cooling processes,” Sievers says. “It is typically a closed system so it is not released into the water, so somewhere they’ve got a breach, a leak, a break, some type of situation with their cooling system that it’s releasing some of the ammonia into the cooling water and, thus, into the discharge.”

Sievers says Wells Dairy has been asked to verify the source of the leak and confirm the release of ammonia has been stopped. State officials say children and pets should stay away from the creek for at least 24 hours. The creek, which is west of Le Mars, is near a ball park that’s south of Highway 3.