Hayden Panettiere’s death is taking an even more tragic turn.

The actress reportedly died after taking a single pill believed to have been oxycodone that was laced with fentanyl, according to law-enforcement sources cited by TMZ.

Panettiere was 36 when she was found dead in a South Carolina apartment on August 16, just days before her 37th birthday.

Authorities have not yet publicly released her official cause of death.

Toxicology testing remains pending, and officials have previously warned that final results could take weeks.

But investigators are now reportedly focusing on where the pill came from — and whether someone supplied Panettiere with the drug before she left Los Angeles.

Sources connected to the investigation told TMZ that Panettiere had allegedly met with a long-term drug dealer in Los Angeles shortly before flying to South Carolina.

She then traveled east with Brian Hickerson, her on-and-off partner, who was with her on the flight and was also present at the apartment where she later died.

The new report suggests Panettiere may have taken just one pill on the day of her death.

Investigators believe it contained fentanyl, the extraordinarily potent synthetic opioid responsible for a huge share of fatal overdoses in the United States.

Fentanyl can be many times stronger than heroin, and counterfeit pills containing unpredictable amounts of the drug have become a major public-health threat.

A pill that appears to be a prescription opioid can contain a lethal dose without the person taking it realizing what is inside.

That is what investigators are now reportedly examining in Panettiere’s case.

Drug Enforcement Administration officials in both Los Angeles and South Carolina are said to be involved.

Reports earlier this month said authorities were “zeroing in” on a possible dealer.

Hickerson has already spoken with DEA investigators, according to multiple reports.

It is not publicly known what he told them.

He had previously told police that Panettiere traveled with a “bag of medication.”

According to the Greenville City Police Department report, the names of the medications were redacted, though investigators documented nine different types.

That detail has become increasingly important as authorities try to reconstruct Panettiere’s final hours.

But the official medical findings are still incomplete.

The coroner has not yet announced that fentanyl caused her death.

That remains a reported investigative theory until the toxicology process is finished.

For those who followed Panettiere’s career, the circumstances surrounding her death are especially painful because she had spoken publicly for years about addiction.

The former child star became internationally known through roles in Heroes and Nashville.

Behind the success, however, she described a far darker struggle.

In interviews and in her memoir, This Is Me: A Reckoning, Panettiere spoke candidly about alcohol and opioid addiction, depression and the pressures she experienced growing up inside Hollywood.

She said her exposure to pills began disturbingly early.

Panettiere told People that when she was about 15, someone on her team gave her what she called “happy pills” before red-carpet appearances.

“They were to make me peppy during interviews,” she recalled.

At the time, she said, she did not understand how dangerous that moment could become.

“I had no idea that this was not an appropriate thing,” she said, “or what door that would open for me when it came to my addiction.”

As her career accelerated, so did her substance-use problems.

Panettiere later described drugs and alcohol as something she reached a point of feeling she could barely live without.

Her struggles intensified after the birth of her daughter, Kaya, in 2014.

Panettiere said she battled postpartum depression and increasingly relied on alcohol.

The physical consequences eventually became severe.

She developed jaundice and was warned that her liver was at risk.

In her memoir, Panettiere said a doctor gave her a terrifying warning:

If she did not stop drinking, she could be dead within five years.

Yet Panettiere also spent years trying to recover.

She spoke openly about treatment.

She returned to acting.

And she increasingly used her own experience to talk about the realities of addiction instead of hiding them.

That makes the latest report even more devastating.

If investigators ultimately confirm that one counterfeit or contaminated pill caused her death, Panettiere’s case would become another stark example of how unforgiving the illicit fentanyl supply has become.

For people with a history of opioid use, the danger can be especially severe after periods of reduced tolerance.

But at this stage, authorities have not publicly released enough information to establish exactly what happened medically.

What is known is that Panettiere died suddenly.

What is reported is that investigators suspect fentanyl.

And what they are now trying to determine is who supplied the pill.

That question could turn a celebrity tragedy into a criminal investigation.

Panettiere’s death has already prompted an outpouring of grief from fans who watched her grow up on screen.

For many, she represented a generation of young actors who achieved enormous fame early, while facing pressures the public rarely saw.

Her own words now sound especially haunting.

She had warned that addiction once made her feel as though she could not live without drugs and alcohol.

Years later, investigators are reportedly examining whether a single pill ended her life.

Until the toxicology results are released, the final medical answer remains pending.

But one thing is already painfully clear:

Hayden Panettiere spent years speaking honestly about how dangerous addiction could become.

And now, investigators believe her final chapter may have come down to just one pill.