DENVER (AP) – The body of a 7-year-old Denver boy found in a storage unit in December showed traces of cocaine and methamphetamine in his liver.

The Denver Post reports the city’s medical examiner determined Caden McWilliams had ingested the drugs before his death.

The elementary school student likely had been dead since May when authorities found his body wrapped in plastic bags and encased in concrete inside an animal crate.

The medical examiner could not determine an exact cause of death but ruled it a homicide.

An autopsy found he was emaciated and weighed about 27 pounds with injuries to his head, torso and extremities resulting in a fractured skull and broken arm.

McWilliam’s mother Elisha Pankey faces charges of child abuse leading to death and abuse of a corpse.