SPIRIT LAKE, Iowa (AP) — Iowa officials say two northwest Iowa lakes have been found to be safe for swimming and boating after fish kills were discovered there earlier this week. The Sioux City Journal reports that dead freshwater drum, a species of fish, washed up on the northwest shore of East Lake Okoboji on Thursday. Fisheries biologist Mike Hawkins with the Iowa Department of Natural Resources says thousands of small fish also washed up on a one-mile portion of Big Spirit Lake the same day.

Hawkins says the kills are not connected. He says the drum were most likely killed by disease spread through overpopulation. He says the small fish died from a pocket of low oxygen on Big Spirit Lake.