Actress Hayden Panettiere died from the toxic effects of fentanyl, Xanax and several other drugs in her system, according to an autopsy by the Greenville County Coroner’s Office in South Carolina.
The coroner’s office classified her death as accidental and found no signs of trauma that contributed to her death.
Panettiere, 36, was found unresponsive at a residence in South Carolina last month. Emergency responders attempted to revive her using advanced cardiac life support measures, but their efforts were unsuccessful.
The autopsy also detected methocarbamol, a prescription muscle relaxant, and quetiapine, an antipsychotic medication used to treat certain mental health conditions.
Panettiere, best known for her roles in the US television series Heroes and Nashville, had previously spoken publicly about her struggles with substance abuse.
She had also discussed her experiences with addiction and postpartum depression in a memoir published just months before her death.
Panettiere said she was first introduced to drugs at around 16 during a red-carpet appearance for Heroes, when a member of her professional team gave her what she was told was a “happy pill” to boost her energy.
She later told People magazine that she initially did not understand the implications of taking the drug, but said drugs and alcohol eventually became something she felt she could not live without.
Fentanyl, a synthetic opioid, is highly potent and has been linked to hundreds of thousands of deaths in the United States in recent years.
The US Drug Enforcement Administration was also reportedly involved in the investigation into Panettiere’s death.
According to a police report from the day she died, her former boyfriend Brian Hickerson and his brother Zack were present when emergency services arrived. Hickerson had previously admitted to abusing Panettiere.
Panettiere’s death came years after the loss of her younger brother, Jansen Panettiere, who died aged 28 from a heart condition.
In her memoir, she wrote about her brother’s own struggles with substance abuse and said he had used heroin and cocaine before his death.
