Owosso issued a no-contact notice for the river because of a sewer overflow caused by the rain.
This advisory is in effect until further notice.
The County Health Department notified state officials at the Department of Environment, Great Lakes, and Energy.
Once the overflow stops, health officials will know how much sewage was discharged directly to the river.
The overflows happen because the collection system is overwhelmed at critical points and are discharged in the river to avoid basement backups for some homes and businesses.
This is the 24th sanitary sewer overflow event in 18 years and the last one was February of 2018.