De Ferran suffers back injury in crash

Doctors confirmed that the Brazilian sustained a minor fracture in his lower spine. He was held overnight at Good Samaritan Regional Medical Center in Phoenix having also sustained a concussion. He was injured when his car collided with Michael Andretti's with 13 laps left and slammed into the wall at Turn 1.

"It was a hard hit," said Andretti, who was not injured. "It was a bad deal."

De Ferran was alert after his crash with Michael Andretti, but the extent of his back and head injuries were not clear immediately following Sunday's race.

"He was able to move," said Helio Castroneves, who visited his team-mate in the infield care center following the race. "I asked if everything was OK, and he said, 'I'm fine, everything's fine.'"

Roger Yasukawa, who led five laps in the early stages of Sunday's race, was also held overnight for observation after sustaining undisclosed injuries when his car crashed midway through the race. He got out of his wrecked car, but appeared to be suffering from a lack of co-ordination.