FLINT, Mich. (AP) — A university professor says conditions in the Flint River were a "recipe" for the bacteria that cause Legionnaires' disease.

Civil engineering professor Shawn McElmurry testified Wednesday at a court hearing for Nick Lyon, the Michigan health director who is charged with involuntary manslaughter and other crimes in the Flint water crisis.

McElmurry says the Flint River had organic matter and iron, which can contribute to legionella. Flint used the river for water in 2014 and 2015.

Lyon is accused of waiting too long to tell the public about a Legionnaires' outbreak during that time. A judge must decide if there's enough evidence to send him to trial.

McElmurry and a team from Wayne State University were hired by the state to study the outbreak. He says Lyon wasn't always in favor of their work.