Federal drug agents are investigating whether a counterfeit oxycodone pill believed to have been laced with fentanyl contributed to the death of actress Hayden Panettiere, as authorities attempt to trace the source of drugs she allegedly obtained before she was found unresponsive in South Carolina.

TMZ reported Sept. 14 that multiple law-enforcement sources connected to the investigation believe Panettiere took what she thought was an oxycodone pill on the morning of her death and suspect the pill contained fentanyl. The outlet reported that investigators are focusing on a person described by its sources as Panettiere’s longtime Los Angeles drug dealer.

But investigators have not publicly established that theory as Panettiere’s official cause of death.

Toxicology results remain pending, and the Greenville County Coroner’s Office has said the investigation is ongoing. Panettiere’s representative has also cautioned against treating reports attributed to unnamed sources as established fact before authorities complete their work.

That distinction is particularly important as the investigation expands from South Carolina to Los Angeles.

Investigators Focus on a Suspected Counterfeit Pill

Panettiere died Aug. 16 at age 36 after being found unresponsive at a residence in Greenville, South Carolina.

According to TMZ, investigators believe Panettiere obtained black-market prescription drugs in Los Angeles before traveling to South Carolina. Sources told the outlet she allegedly took several drugs during the trip and then took what she believed was oxycodone on the morning she died.

Investigators suspect that final pill may have contained fentanyl.

TMZ's sources described the fentanyl-laced oxycodone theory as investigators' current working explanation for her death, but acknowledged that toxicology results are critical to determining whether that theory is correct.

The distinction between a legitimate prescription oxycodone tablet and a counterfeit pill is significant.

Illicit pills can be manufactured to resemble prescription medications while containing fentanyl, a powerful synthetic opioid. A person taking such a pill may not necessarily know fentanyl is present.

At this stage, authorities have not publicly released laboratory findings establishing exactly what substances were in Panettiere's system.

DEA Investigation Reaches Los Angeles

The investigation has moved well beyond the South Carolina residence where Panettiere died.

TMZ subsequently reported that DEA agents executed a search warrant at Panettiere's Los Angeles home on Aug. 25, nine days after her death. Agents were reportedly searching for evidence involving black-market controlled substances, including drugs that could be tested for fentanyl and other material potentially identifying where the substances originated.

The search provides another indication that federal investigators are attempting to reconstruct how Panettiere obtained the drugs she allegedly possessed before traveling across the country.

According to TMZ, DEA investigators in Los Angeles and South Carolina are working on the case as authorities attempt to determine where the suspected pill originated and whether it can be traced to a supplier.

No publicly announced criminal charge has established that any particular person supplied Panettiere with a fatal drug.

Narcan Administered Before Paramedics Arrived

The circumstances surrounding Panettiere's final moments are also part of the investigation.

Police records and subsequent reporting show that Panettiere was found unresponsive at the Greenville residence on Aug. 16. Her boyfriend, Brian Hickerson, reportedly administered Narcan before emergency personnel arrived, but she could not be revived.

First responders performed CPR before Panettiere was pronounced dead at 2:31 p.m.

An initial autopsy found no signs of trauma, according to reporting citing authorities, leaving toxicology as a crucial part of determining what caused her death.

Investigators were also provided with a bag containing medications Panettiere had reportedly been taking. What those medications contained—and whether any were connected to her death—remains part of the investigation.

Panettiere’s Representative Pushes Back

As reports about fentanyl and an alleged drug supplier spread online, Panettiere's representative urged caution.

Her team said there had been conflicting information circulating from unnamed sources and emphasized that the investigation had not been completed. The representative described some of the reporting surrounding the case as unverified and said Panettiere's loved ones were cooperating with authorities while waiting for definitive answers.

The Greenville County Coroner's Office has similarly maintained that the death investigation remains open while toxicology testing is completed.

That means reports describing Panettiere's death definitively as a fentanyl overdose currently go further than the official findings support.

What can be reported is that law-enforcement sources say investigators suspect a fentanyl-laced pill, federal agents are attempting to trace the drugs involved, and the DEA searched Panettiere's Los Angeles residence as part of that investigation.

Whether fentanyl actually caused her death remains awaiting official toxicology findings.

Investigation Continues Across Two States

The investigation now has two geographic centers.

South Carolina authorities are examining the circumstances surrounding Panettiere's death, while federal investigators in Los Angeles are pursuing the alleged drug supply chain that may have preceded it.

For investigators, the central questions are increasingly clear: what exactly did Panettiere take, where did it come from, and did an illicitly manufactured pill contain fentanyl without her knowledge?

TMZ's law-enforcement sources believe they have a working theory.

The official toxicology report will determine whether the evidence supports it.

Until those results are released, Panettiere's precise cause of death remains under investigation.