Nearly a month after Hayden Panettiere was found unresponsive inside a South Carolina residence, investigators still do not have a publicly announced answer to the central question surrounding her death.

But the investigation is expanding.

Brian Hickerson, Panettiere’s on-again, off-again boyfriend, has met with officials from the Drug Enforcement Administration as federal authorities assist in examining the circumstances surrounding the actress’s sudden death at age 36, a source close to the investigation told PEOPLE.

Authorities have also interviewed other people, according to the source.

And investigators are reportedly pursuing another potentially significant lead: whether someone supplied Panettiere with drugs shortly before she died.

The development does not mean Hickerson has been accused of supplying her with drugs or causing her death. He has not been named a suspect, and no criminal charges have been announced against him in connection with the case.

For investigators, one crucial piece of evidence remains outstanding.

Panettiere’s toxicology results have not yet been completed.

Panettiere Was Found in Cardiac Arrest

Panettiere died on Sunday, Aug. 16, at a residence in Greenville, South Carolina.

Police responded after receiving a 911 call reporting an “unresponsive female.”

First responders attempted to save her, but she was ultimately pronounced dead.

The Greenville County Coroner’s Office performed an autopsy the following day. Coroner Mike Ellis said Panettiere had been found in cardiac arrest and that investigators discovered no signs of trauma that would have contributed to her death.

Her death nevertheless remained under active investigation.

With no obvious traumatic cause identified, toxicology testing became especially important.

Those results may reveal whether alcohol, prescription medications, illicit substances or some combination of factors was present in Panettiere’s system.

Until that testing is completed and reviewed alongside the rest of the evidence, authorities have not publicly established an official cause of death.

Why Is the DEA Involved?

The latest development centers on federal drug investigators.

A source confirmed to PEOPLE that Hickerson met with the DEA and said authorities have “interviewed others” during the investigation. The DEA itself had not publicly commented on the meeting when PEOPLE published its report.

TMZ, which first reported Hickerson’s meeting with the agency, said investigators are attempting to identify a person who allegedly may have sold Panettiere drugs that could have contributed to her death.

One source told the outlet that investigators were “zeroing in on a potential drug dealer.”

That remains an investigative theory rather than a confirmed conclusion.

Investigators have not announced that drugs caused Panettiere’s death, and the pending toxicology results could prove essential in determining whether that theory is supported.

The involvement of the DEA also does not automatically mean anyone who was with Panettiere at the residence is suspected of a crime.

Hickerson, specifically, has not been named a suspect.

His attorney, Sloan Ellis, declined to comment to PEOPLE about the reported DEA meeting. In an earlier statement, Ellis emphasized that the investigation should be allowed to continue before conclusions are reached.

Hickerson and His Brother Were at the Residence

Hickerson’s presence during the emergency has been known since shortly after Panettiere’s death.

According to a police report obtained by PEOPLE, Hickerson and his brother, Zach, were both at the Greenville residence when first responders arrived.

Hickerson showed officers a bag containing medication Panettiere had been taking.

The responding officer also documented the reactions of the two brothers. Zach was described as highly emotional during the attempts to revive Panettiere, while the officer wrote that Brian did not visibly become emotional until Panettiere had been declared dead.

Zach referred to Panettiere as his brother’s “girlfriend,” according to the report.

Those observations are part of the police record, but authorities have not publicly presented them as evidence of wrongdoing by Hickerson.

That distinction is important given the attention surrounding their complicated relationship.

Their Relationship Had a Troubled History

Panettiere and Hickerson were first romantically linked in 2018, following her separation from former fiancé Wladimir Klitschko, with whom she shared daughter Kaya.

Their relationship later became connected to several serious domestic violence cases.

Hickerson was arrested on domestic violence-related charges in 2019 and again in 2020.

After the 2020 arrest, Panettiere issued a public statement saying she was speaking about what had happened in hopes of helping other people in abusive relationships seek help.

In 2021, Hickerson pleaded no contest to two felony counts of injuring a partner stemming from his 2020 arrest. He received four years of formal probation, domestic violence classes, a protective order and a 45-day jail sentence, of which he served 13 days. Other charges were dropped, while the separate 2019 case was dismissed.

Despite that history, Panettiere and Hickerson were later again seen together, and the police report from Aug. 16 indicated they were still connected at the time of her death.

A Court Hearing Happened Just Three Days Earlier

Another detail has drawn attention because of its timing.

On July 20, Hickerson filed a petition seeking to have his previous felony convictions expunged, arguing that he had completed the requirements of his probation.

A hearing concerning that request took place on Aug. 13 — three days before Panettiere died.

According to court records obtained by PEOPLE, prosecutors opposed the request and cited allegations of continued drug use by Hickerson.

Neither Hickerson nor his attorney attended that hearing.

Those allegations relate to Hickerson’s own legal proceeding and do not establish what happened to Panettiere three days later.

Investigators have not publicly linked that hearing to her death.

Panettiere Had Previously Spoken About Addiction

Panettiere herself had been candid about her past struggles with alcohol and opioids.

In a 2022 interview with PEOPLE, she described an earlier period of her life as “very dark and complicated.”

She said that during that period she wanted to party and engage in behavior she knew was harmful.

Her willingness to discuss addiction publicly became an important part of her story as she attempted to rebuild both her personal life and acting career.

But a history of addiction alone cannot establish what caused someone’s death years later.

That is why the toxicology evidence matters so much.

Investigators must determine what substances, if any, were present in Panettiere’s body and whether they played a role in the cardiac arrest reported by the coroner.

A Career That Began in Childhood

Panettiere had spent most of her life in front of cameras.

She began acting as a child and appeared in projects including Remember the Titans before becoming internationally recognizable as Claire Bennet, the indestructible cheerleader at the center of NBC’s Heroes.

She later earned acclaim for playing troubled country singer Juliette Barnes on Nashville.

Her family announced her death in an emotional statement, remembering her as “an incredible light and a force of nature” who brought love and joy to both the people who knew her personally and millions who watched her onscreen.

Panettiere is survived by her daughter Kaya, now 11.

The Biggest Answer Is Still Missing

Nearly a month after Panettiere’s death, investigators have accumulated several pieces of the puzzle.

An autopsy has been completed.

No contributing trauma was found.

Police have interviewed people who were present.

Federal drug investigators are now involved.

Hickerson has met with the DEA.

And authorities are reportedly attempting to determine whether a drug supplier played any role in what happened.

But none of those developments answers the most important question by itself.

The toxicology report is still pending.

Until those results are returned — and investigators determine how they fit with witness interviews, Panettiere’s medications and the other evidence collected from her final hours — reports about drugs remain part of an active investigation rather than an established cause of death.

For now, Hickerson’s meeting with the DEA represents an important new step.

It does not represent a finding of guilt.

And somewhere in the evidence investigators are still gathering may be the answer Panettiere’s family and fans have been waiting for since Aug. 16:

what caused a 36-year-old actress to suddenly go into cardiac arrest — and whether another person played any role in the events that led to it.