Race officials say the drivers were about midway through their main event Saturday night, when the number one sprint car driver in New Zealand, Peter Murphy, collided with another vehicle.
"There was contact with another car. They were going down the front stretch and sometimes these things are open wheel cars and stuff like that happens. You make contact. We've seen it a lot. He and another car got together and sent him upside down, down the front straight away and he ended up landing in turn one," Promoter Gary Thomas said.
It took emergency crews about 40 minutes to free Murphy.
He's now recovering at John Muir medical center.