Hayden Panettiere had recently completed a stint in rehab and was surrounded by drug paraphernalia when she was found unresponsive last month in an Airbnb in South Carolina, according to a newly released coroner’s report. On Tuesday, the coroner’s office announced the exact cause of her death — a toxic mixture of the powerful opioid fentanyl, anti-psychotic and anti-anxiety drugs and a muscle relaxant.

The latest report, obtained by The New York Times on Wednesday, said that on Aug. 16, a senior deputy coroner attended the scene at the Airbnb apartment in Greenville, S.C., shared by Ms. Panettiere, her on-again off-again boyfriend Brian Hickerson, and his brother, Zach Hickerson. The investigator found a small, clear plastic bag with blue tablets that appeared to be pills and a cut straw, which later tested positive for fentanyl. The investigator also found multiple prescription bottles on a kitchen table; a small lunch box with glass vials, prefilled and empty syringes in the refrigerator; and a small, clear plastic bag containing an unidentified white powdery substance inside a gray sunglass case.

Her death, days before her 37th birthday, was ruled an accident and the autopsy found no signs of trauma that could have contributed to it. The report said that a man in the apartment had witnessed Ms. Panettiere applying makeup around 10 a.m. that morning and then they ate a bowl of cereal together before he fell back asleep. She was found that afternoon wearing a yellow sweatshirt and jogging pants and sitting with her legs crossed, face down and unresponsive on a sofa bed. Brian Hickerson noticed she was turning purple, the report added, and administered two doses of nasal Narcan before calling 911.

When emergency medical workers arrived at the scene, according to a police statement last month, they administered advanced cardiac life support and resuscitation efforts for 30 minutes without success. The actress, best known for her roles on “Heroes” and “Nashville,” was then pronounced dead. The latest report outlined a conversation between the investigator and a man at the scene who said Ms. Panettiere had a history of drug, alcohol and nitrous oxide abuse and that she had recently been in a drug rehab facility in Malibu, Calif. The other drugs found in Ms. Panettiere’s system included alprazolam, the generic version of Xanax, methocarbamol, and quetiapine.