Four people were hurt when a motorcyclist performing a stunt accidentally drove into a crowd at the annual Sturgis Motorcyle Rally, said a spokeswoman for the South Dakota campground where the event is held.

Buffalo Chip Campground spokeswoman Nyla Griffith told the Rapid City Journal the accident happened around 9:45 p.m. Sunday between performances by Lita Ford and Kid Rock. She said a rider was performing a burn out between shows when he lost control and went off stage.

Griffith said four people were treated on the scene and were believed to have been taken to a hospital. The extent of their injuries wasn't immediately clear.

This year's annual Sturgis rally in western South Dakota's Black Hills kicks off Monday. A record 739,000 people attended last year.