Four-time IndyCar Series champ Dario Franchitti fractured his spine in a spectacular crash during the final lap of the Houston Grand Prix that was won by Will Power.
The Scotsman's injuries also included a broken right ankle and a concussion, said IndyCar's head of medical services Michael Olinger.
Olinger said Franchitti's spinal fracture would not require surgery.
Franchitti "was admitted awake and alert to Memorial Hermann Texas Medical Center in Houston for a concussion and spinal fracture that will require no surgery and a fracture to the right ankle. He will be kept overnight," Olinger said.
Franchitti's car went airborne Sunday after colliding with Takuma Sato and slammed into the safety fencing before coming to a halt in the middle of the street circuit track.
He was stretchered off the track and taken by ambulance to the nearby hospital.
Franchitti's team owner Chip Ganassi spoke to the driver at the crash site.
"His ankle is a little sore, his back is a little sore. He is going to be OK," said Ganassi.
The three-car smash happened in turn five of the track's 10 turns and also involved Japan's Sato and E. J. Viso of Venezuela, but they were both able to exit their cars and walk away.
"On the last lap I caught the marbles and brushed the wall and lost momentum," said Sato. "A couple cars passed me as I was offline and in turn five. I got very loose and Dario and I came together."
Debris from the crash also flew over the top of the safety fencing, injuring about a dozen spectators.
"Dario Franchitti along with two fans were transferred to an area hospital for evaluation. Eleven fans were treated on site," Mi-Jack Productions, the promoter of the race said in a news release.
"Officials are investigating the incident."
Race officials were forced to postpone Friday's qualifying because of problems with the 2.57 kilometer (1.6 mile) temporary street circuit which included a troublesome bump in turn one.
Qualifying finally got underway Saturday morning, but not before track crews worked overnight and into the morning grinding the area in turn one to try and make it safe for the drivers.
Franchitti, 40, hit the back of Sato's race car and was propelled into the air and against the fence. The car exploded into several pieces but did not catch fire.
Three-time Indianapolis 500 winner Franchitti remained in the car for a minute until rescue personnel arrived. They removed him from the vehicle and put him on a stretcher before he was taken away.
Power scored his second victory of the season after he held off New Zealand driver Scott Dixon, who had won Saturday's first race of the weekend double header.