Two people were killed Saturday evening at Marysville Raceway Park when a sprint car careened at high speed over a wall and into the pit area.
Yuba County Sheriff's Department officials said a 68-year-old man was pronounced dead at the scene, and a 14-year-old was pronounced dead later at Rideout Memorial Hospital.
The names of the two victims were not being released Saturday night, sheriff's Capt. Ron Johnson said.
Track announcer Steven Blakesley told ABC News the 14-year-old was the driver's cousin and the older victim owned several race cars.
Marysville track promoter Paul Hawes confirmed the two people who were struck are part of the driver's family and crew, but he declined to identify them.
Blakesley named the driver in several tweets as 17-year-old Chase Johnson, a high school senior from Petaluma. He was uninjured, sheriff's officials said. Johnson has been in more than 500 races, beginning at age 4, according to his website.
The crash occurred at 6:04 p.m. during warmup laps for the first race of this year's California Sprint Car Civil War Series. The race was canceled.
Hawes said the driver lost control in the first turn, went over a retaining wall and slid 100 feet along a K-rail barrier before hitting the victims. No one else was reported injured.
Announcer Blakesley immediately tweeted the incident.
"We have had a very serious accident. Chase Johnson had a problem and flew into the pits. Several people appear to be injured."
Yuba Sheriff's Capt. Johnson said deputies were uncertain late Saturday what caused the crash. Blakesley speculated in a tweet that Johnson's car may have had mechanical problems because it did not slow down.
Blakesley later reported, "The drivers have got together and agreed to donate all the back gate money to the families."
Marysville Raceway Park is a quarter-mile banked clay oval a mile east of Marysville near the town of Linda.
Call The Bee's Tony Bizjak, (916) 321-1059. Follow him on Twitter @tonybizjak. Bee correspondent Mark Billingsley contributed to this report.