Michael Baze, a promising jockey who was born in Renton, was found dead in his vehicle Tuesday at Churchill Downs. Mr. Baze, 24, who lived...

LOUISVILLE, Ky. — Michael Baze, a promising jockey who was born in Renton, was found dead in his vehicle Tuesday at Churchill Downs.

Mr. Baze, 24, who lived in Glendora, Calif., was pronounced dead at 4:47 p.m. EDT in his vehicle parked in the stable area of the track, Jefferson County Deputy Coroner Jim Wesley said.

There were no signs of foul play and the case was being treated as a death investigation, Louisville police spokeswoman Alicia Smiley said. An autopsy was planned.

Mr. Baze was a cousin of Hall of Fame jockey Russell Baze, the winningest rider in North American Thoroughbred racing, and son of retired jockey Mike Baze, who rode at Longacres in Renton. He was a nephew of Northwest riding legend Gary Baze.

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“Somebody coming out of that family, it always gets your attention when you see the Baze name,” Churchill Downs spokesman John Asher said.

Mr. Baze rode Nehro, Saturday’s Kentucky Derby runner-up, to a victory Feb. 21 at Oaklawn Park in Hot Springs, Ark. He was scheduled on at least one mount Thursday at Churchill Downs, Asher said.

His last mount was April 29 at Keeneland in Lexington, Ky.

Mr. Baze, who had been riding since he was 16, was the leading rider at Arlington Park in suburban Chicago last summer. He had 6,968 career starts with 918 wins, and his mounts earned more than $32 million.