Hayden Panettiere's Cause of Death Revealed as Toxic Effects of Fentanyl, Quetiapine and Other Drugs — Weeks After Actress Was Found Unresponsive

Hayden Panettiere died from the combined effects of five different drugs, RadarOnline.com can exclusively reveal, including fentanyl.

The Greenville County Coroner's Office in South Carolina has released the results of its toxicology testing, which concluded the Heroes star's death was "accidental."

Panettiere died Sunday, August 16, of what was initially ruled a heart attack.

However, Radar has obtained a copy of the coroner's report, which concluded the 36-year-old's "cause of death has been ruled as toxic effects of fentanyl, 4-ANPP, Alprazolam, Methocarbamol, and Quetiapine.

An autopsy was completed by a board-certified forensic pathologist with the Greenville County Coroner’s Office.

Coroner Mike Ellis ruled her death an accident after "no signs of trauma were discovered" in the autopsy "that would have contributed to the death."

The Nashville star was reportedly given the drugs by her "long-term drug dealer," who is now at the center of a police investigation.

The star reportedly met her dealer in L.A. before flying to South Carolina, where she died of a suspected overdose just before her 37th birthday. She and the dealer apparently exchanged text messages to orchestrate the exchange.

"There are a slew of messages about drugs," a source involved in the investigation told TMZ about Panettiere's alleged incriminating electronic exchanges with her dealer, in which they were "very specific about purchasing black-market pills."

Sources told the outlet that she appeared to have taken one pill the day she died, but it was fatal as it was laced with fentanyl, which is 50 times stronger than heroin.

Panettiere’s ex-boyfriend Brian Hickerson — who was with her in the South Carolina apartment where she died — has already met with DEA officials as part of the probe into her shocking death.

He previously told officials Panettiere had a "bag of medication" with her when she died.

Hickerson has reportedly been having an especially difficult time dealing with Panettiere's death. According to TMZ, Brian has lost about 40 pounds since the actress died and has struggled to regain a "sense of normalcy."

Sources claimed he still has moments when he expects her to call him.

During those moments, he reportedly feels as though the entire situation could somehow turn out to be a "horrible dream."

When the 37-year-old was asked by a photographer how he was coping with Panettiere's death, he shrugged back, "How do you think I’m doing?"

After the photographer offered his condolences, Brian responded, "Appreciate it. That's all I got for you, man."

Panettiere's family and friends gathered over the weekend at a church in Malibu for a private celebration of life for the actress.

The coastal location chosen to host the event had a personal connection to Panettiere, who was known to love the ocean and whales.

Around 150 family members, close friends and former colleagues packed the church to honor her. Her father, Skip Panettiere, was reportedly present, but her mother, Lesley Vogel, was not invited.

The 70-year-old said she believes her daughter and Hickerson had a toxic "codependent bond" that became increasingly difficult for her family to break.

Hickerson was missing from the memorial as well.