Sprint car driver Kevin Swindell suffers 'significant injury' in crash

KNOXVILLE, Iowa -- The family of sprint car driver Kevin Swindell said Friday that he suffered "a significant injury" Thursday after his car flipped at the start of a heat race at the Knoxville Nationals.

Swindell's father, sprint car great Sammy Swindell, said in a series of tweets Friday that his son had undergone surgery at Des Moines Mercy Hospital.

Kevin Swindell's car flipped, hit an outside wall and landed on its wheels at the World of Outlaws event Thursday. Swindell, 26, was airlifted to the hospital.

The family had previously thanked the Knoxville Raceway safety team for their quick response and the support of the racing community.

Swindell, from Germantown, Tennessee, also races stock cars, winning twice in the ARCA Racing Series and competing in the NASCAR Xfinity Series.

The Associated Press contributed to this report.