LE MARS, Iowa — The Iowa Department of Natural Resources says a fish kill in a northwestern Iowa stream has been traced to a Le Mars ice cream making plant.

The department says ammonia from the Wells Enterprises plant, which makes Blue Bunny ice cream, found its way into the Plymouth County stream, killing a large number of minnow and chubs.

Officials say the ammonia was in cooling water discharge from the plant.

The department said Friday it will continue to look for and verify the spill source and send water samples for laboratory analysis. DNR fisheries staff also planned to do a fish kill count Friday.