Hayden Panettiere's cause of death revealed one month after star died aged 36

Hayden Panettiere's cause of death has been officially confirmed, one month after the star died aged 36. 

Panettiere died August 16 at a residence in Greenville, South Carolina, in what authorities said was suspected as a drug 'overdose.' 

Her on-off boyfriend Brian Hickerson and his brother, Zach, were both at the scene when Panettiere was pronounced dead.

Now, a spokesman for the Greenville County Coroner’s Office has confirmed to The Daily Mail that Panettiere died from the 'toxic effects' of multiple drugs - including fentanyl - and that her death was accidental.

Just a few grains of powerful opioid fentanyl, which is 50 times stronger than heroin, can cause a fatal overdose.

A spokesman said, 'An autopsy was completed by a Board Certified Forensic Pathologist. At autopsy no signs of trauma were discovered that would have contributed to the death.

'The cause of death has been ruled as toxic effects of fentanyl, 4-ANPP, Alprazolam, Methocarbamol, and Quetiapine. The manner of death has been ruled accident.

'This case is administratively closed by the Greenville County Coroner’s Office.'

Methocarbamol is a prescription muscle relaxant used to treat short-term muscle pain, while Quetiapine, commonly known by the brand name Seroquel, is an antipsychotic prescription medication used to treat conditions including schizophrenia, bipolar disorder, and major depressive disorder.

Alprazolam, known as Xanax, is used to treat anxiety and panic disorders and 4-ANPP is a chemical used as a main building block to make illegal fentanyl.

Last week, insiders told TMZ authorities believed Panettiere had fatally consumed a single oxycodone pill laced with fentanyl. 

Panettiere had a 'long time drug dealer' in Los Angeles who she obtained narcotics from illegally, with oxycodone among them, sources told the outlet.

Authorities said that the day prior to her passing, Panettiere had taken multiple drugs she bought in Los Angeles before flying to South Carolina, where she was found dead the next day.

Panettiere's rep said in a statement earlier this month, 'As reported yesterday by the Greenville County Coroner's Office, Hayden's death remains under investigation pending the completion of toxicology results, despite reports from some outlets stating otherwise.

'Recent reports attributed to unnamed sources are unverified hearsay and have attributed to conflicting information that continues to circulate.'

The statement continued: 'While we are all eager to find closure and better understand the circumstances surrounding her passing, we must remain patient and allow the investigative process to unfold.'

The late Heroes star's rep concluded in saying that 'the answers we are all seeking will come.'

On the day she died, first responders arrived at a Greenville, South Carolina, condo where attempts were made to resuscitate the actress, before she had been pronounced dead.

Hickerson's lawyer Sloan Ellis said in a statement August 20 that 'Hayden's death remains under investigation and it is important to allow that investigation to proceed.

'As has been publicly reported, police confirmed there were no signs of foul play. Out of respect for Hayden's loved ones and the ongoing investigation, there will be no further comment at this time.'

Panettiere began acting as a child, appearing in soap operas, then gained wider recognition for her role in the 2000 sports drama Remember the Titans with Denzel Washington, and as the voice of Dot in Pixar's 1998 film A Bug's Life.

Panettiere later found fame playing cheerleader Claire Bennet in the superhero drama Heroes before starring as country singer Juliette Barnes for six seasons on Nashville.

She earned two Golden Globe nominations for best supporting actress on the show, while her singing produced 11 entries on the US Billboard Hot Country Songs charts.

Panettiere's film credits include 2006's Bring It On: All or Nothing, the comedy-drama film Raising Helen, and appearances in Scream 4 and Scream VI as Kirby Reed.

She had an 11-year-old daughter called Kaya following a life-threatening birth, and later gave full custody of the child to her former fiancé, Ukrainian boxer Wladimir Klitschko.

Panettiere's passing was announced by her father Skip Panettiere, who said in a statement: 'It is with profound sadness that we share the tragic passing of our beloved Hayden.

'She was an incredible light and a force of nature who brought immeasurable love and joy to all who knew her - and to the millions who watched her onscreen. We ask for privacy as our family takes time to process this unimaginable loss.'

Authorities in Greenville, South Carolina, subsequently said that officials responded to an apartment in the area after receiving a report of an 'unresponsive female' via a possible 'drug overdose,' subsequently determined to be Panettiere.