Jenner was driving a black Cadillac SUV that was the third vehicle involved in a multiple read-end collision, Sgt. Philip Brooks of the sheriff's department said.
The first vehicle was a black Prius that stopped short, CNN affiliate KCAL reported
, citing deputies. Behind it was a white Lexus sedan that also hit its brakes.
Jenner's Escalade was towing a trailer with an all-terrain vehicle on it when it ran into the Lexus from behind, Brooks said. The Lexus spun into oncoming traffic and was hit by a Hummer H2. The driver of the Lexus was killed.
KCAL reported Jenner's SUV left skid marks.
The midday wreck came just after noon on Pacific Coast Highway near Corral Canyon Road, the department said in a news release.
The sheriff's department later opened a vehicular manslaughter investigation, a source close to the case told CNN legal analyst Mark Geragos. The investigation will focus on everyone in the case, not just one person, the source said.
The sheriff's department said on its Facebook page that the surviving drivers were cooperating with investigators.
A deputy said Jenner voluntarily took a field sobriety test, was questioned and went home.
No information about the deceased was immediately available.
Jenner, 65, was not injured in the crash, publicist Alan Nierob said.
Pictures posted by TMZ showed Jenner standing by a damaged car talking with a firefighter.
Five children and two adults were taken to the hospital with injuries, authorities said.
The sheriff's department is still investigating the cause of the accident, the statement said. The accident occurred on a tricky stretch of the highway, where the road is narrow and twisting.
In a bizarre twist to the story, a car later drove through safety barriers around the scene and struck two of the cars from the initial accident, Cmdr. Mike Parker of the sheriff's department tweeted. The driver was arrested on suspicion of driving under the influence, Parker wrote.
Jenner won the 1976 Olympic decathlon with a world record score for the 10-discipline event. He quickly capitalized on his success with Wheaties commercials, appearances and other ventures.
He became an actor, appearing in the drama "CHiPs" in 1981 and occasionally playing himself on shows such as "Silver Spoons." He is best known to many television viewers as a member of the cast of the current reality show "Keeping Up With the Kardashians."