Drew Barrymore's Half-Sister Jessica Found Dead

— -- Drew Barrymore's half-sister has died.

Jessica Barrymore, who, like the actress, was the daughter of actor John Barrymore, would have turned 48 on Thursday.

"Although I only met her briefly, I wish her and her loved ones as much peace as possible," Drew Barrymore told ABC News in a statement. "I'm so incredibly sorry for their loss."

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According to the San Diego County Medical Examiner's Office, Jessica Barrymore was found in her car and shortly thereafter, the fire department confirmed that she was dead.

A cause of death has not yet been determined.