Southern Indiana spokesman Dan McDonnell says witnesses saw Lewis hit his head when he fell under the basket with about 4 minutes left in Thursday night's game. He was rushed to an Owensboro, Ky., hospital where he died about 10 p.m.
An autopsy was scheduled for Friday morning. The school scheduled a news conference for Friday afternoon.
McDonnell says he isn't aware of any preexisting medical conditions that could have contributed to Lewis' collapse.
Lewis was from Fort Wayne, Ind., where he led the state in rebounding as a high school senior as a center. He is survived by his infant son, fiancee, mother and sister.