Motes' body was discovered in a bathtub Sunday in Los Angeles at a home where she was pet sitting, the New York Daily News reports.
The Los Angeles County Coroner's Office is working to determine the cause of death. An official told the Daily News that both prescription and non-prescription drugs were found at the scene.
Motes, 37, did not leave a visible note at the scene, and there were no signs of foul play, a law enforcement source told the Daily News.
Roberts' family confirmed the tragedy in a statement posted Monday by People magazine:
"It is with deep sadness that the family of Nancy Motes ... confirms that she was found dead in Los Angeles yesterday of an apparent drug overdose," the statement reads. "There is no official report from the Coroner's office yet. The family is both shocked and devastated."
On the Red Carpet reports that Motes, 37, shared a mother with Julia, 46, actor Eric Roberts, 57, and another sister, Lisa. Eric and his daughter, "American Horror Story" actress Emma Roberts, have not commented about the tragedy, OTRC reports.
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