ST. PAUL — As Minnesota’s lakes start to freeze, safety officials are warning outdoor enthusiasts to be cautious when venturing out onto any lake that’s covered or partially covered with ice, especially those with aeration systems.

Aerators are installed on around 280 Minnesota lakes to help prevent winterkill of fish. But they also create areas of open water and thin ice that are hazardous to anglers, snowmobilers and skiers.

DNR aquatic biologist Marilyn Danks said open water areas created by aeration systems can shift or change shapes depending on weather conditions. And she said leaks may develop in air lines, creating new areas of weak ice or open water.

Aerated lakes are required to have warning signs at all commonly used access points, along with thin ice signs marking the area’s perimeter.