The crash was apparently triggered when driver Regan Smith's car, which was being tailed by Brad Keselowski on his back bumper, spun to the right and shot up the track.
Smith had been in the lead and said after the crash he had been trying to throw a "block."
Larson's car slammed into the wall that separates the track from the grandstands, causing his No. 32 car to go airborne and erupt in flames.
When a haze of smoke cleared and Larson's car came to a stop, he jumped out uninjured.
His engine and one of his wheels were sitting in a walkway of the grandstand.
"I was getting pushed from behind," Larson told ESPN. "Before I could react, it was too late."
Tony Stewart pulled out the win, but in victory lane, what would have been a celebratory mood was tempered by concern for the injured fans.
"We've always known this is a dangerous sport," Stewart said. "But it's hard when the fans get caught up in it."
The Associated Press contributed to this report.