Kevin Orton, a junior-varsity coach at Santa Margarita High School, has become the school's third coach to be arrested on drug possession charges.
Orange County Sheriff's investigators say deputies spotted Orton in a limousine last weekend in San Juan Capistrano.
Orton, who lives in Costa Mesa, was arrested for being under the influence and possession of a controlled substance.
"They found a bag in the limo containing a white powdery substance, ran tests in the field and determined it to be cocaine," said Orange County Sheriff's Department Spokesman Jim Amormino.
Orton declined to talk to Eyewitness News. Orton is no longer employed by the school.
In addition to the three coaches, Santa Margarita's varsity head coach, Harry Welch, is under investigation for allegedly shoving a player in December. Welch led Santa Margarita to CIF and state bowl titles in December.
