A fish kill is under investigation in northwest Iowa. Bryon Whiting, with the Iowa D.N.R. field office in Spencer, says a resident noticed the West Branch of the Floyd River looked “murky” and called the D.N.R. on Monday.

“It looks like we have some high levels of ammonia in the stream and the last information I had was there were hundreds of dead fish,” Whiting said. The fish kill is located about two-and-a-half miles south of Sioux Center. The source of the ammonia is unknown.

“Ammonia is one of those things that can come from about anywhere, so we have to look at all possible sources,” Whiting said. The dead fish are still being counted, but Whiting said they’ve been located as far as five miles downstream.