San Bernardino County fire sent seven ambulances and 10 air ships to the scene of the accident at the California 200 race in Lucerne Valley.
Authorities said a dozen people were airlifted to hospitals in the area, one possibly being Desert Valley Hospital in Victorville.
According to published reports, winesses saw a pickup hit people who were sitting on rocks.
The California Highway Patrol has taken the lead and has sent its Major Accident Investigation Team in.
According to the Mojave Desert Racing website, the California 200 was to take place Saturdayat 7:30 p.m. off Bessemer Mine Road at Soggy Dry Lake.
Amateur video on the internet of last year's race shows off-road vehicles performing stunts close to spectators with only plastic netting between them.