The excessive heat during yesterday's Chicago Marathon took a toll on the thousands of runners who participated. One runner died during the race, though it was supposedly not heat related.

A 35-year-old Michigan police officer, Chad Schieber, collapsed around the 19 mile mark. An autopsy showed he died of mitral valve prolapse, the medical examiner said.

More than 300 runners in the Chicago Marathon sought out medical treatment for heat-related conditions. Two are still in the hospital in critical condition.