Clean-up continues for a fertilizer spill that happened last Thursday at a northeast Iowa coop.

According to news release from the Iowa Department of Natural Resources, an employee of the Farmers Coop in Allison was pulling a tank of liquid nitrogen fertilizer when a seam on the tank split open. It spilled about 800 gallons of the fertilizer on a city street. Coop employees decided to divert the liquid into a storm sewer.

The coop notified state officials 26 hours after the spill happened. On Friday afternoon DNR staff discovered dead minnows for about half a mile downstream from the storm sewer. On Saturday, state officials asked the coop to build a dam across a drainage ditch to contain and pump out the contaminated water. Testing along an eight-mile stretch of the stream, which drains into the West Fork of Cedar River, “showed elevated levels of ammonia in spots” on Friday afternoon, but state officials say “ammonia levels dropped significantly over the next three days.”

A statement from the state agency indicates DNR staff are monitoring the clean-up and “appropriate” fines will be considered later.