Renfro -- who starred in "The Client," "Apt Pupil" and "Bully" -- was found dead in his home Jan. 15. He was 25.
TMZ.com said the cause of his death was declared "acute heroin/morphine intoxication."
"The final manner of death has been ruled an accident," the coroner told the celebrity news Web site.
Ray Liotta sues skin care company over use of likeness
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