MILWAUKEE (AP) -- The National Weather Service has extended heat warnings for parts of Wisconsin into Saturday -- after days of excessive temperatures that reached into the 100s.

The high heat has been blamed for three deaths in Wisconsin and is suspected in a fourth.

Heat-related deaths were reported in La Crosse, Lone Rock and Janesville. The death of an Onalaska man is also being investigated as possibly related to the heat.

The Milwaukee Journal Sentinel reports that a heat warning was supposed to expire Friday but was extended. Southern Wisconsin lakeshore counties are now in an excessive heat warning through Saturday morning, while inland counties are under a heat warning until Saturday afternoon.

The heat has also caused highways across the state to buckle.