(CNN) -- Three-time Indianapolis 500 winner Dario Franchitti was injured in a serious crash that also left 13 spectators hurt during Sunday's Grand Prix of Houston, authorities reported.
The wreck occurred in the last lap of the race, when Japanese driver Takuma Sato bumped Franchitti's car, sending it airborne into the protective fencing. The car spun multiple times against the fence, sending shards of debris flying toward the grandstands and shearing off part of its side.
Two of the 13 spectators injured were sent to local hospitals, while the rest were treated at the scene, according to Senior Capt. Ruy Lozano of the Houston Fire Department.
Franchitti, 40, suffered a concussion in the wreck and fractures to his spine and ankle. The spinal fracture does not require surgery, according to Dr. Michael Olinger, director of medical services for IndyCar. Franchitti will be kept overnight at Memorial Hermann-Texas Medical Center in Houston.
The Scotland native won IndyCar racing's top prize in 2012, 2010 and 2007. He was married to actress Ashley Judd for more than 11 years, but the couple announced in January that they were ending their marriage.
Judd tweeted Sunday evening that she was on her way to Houston, thanking fans for their prayers.