The federal Drug Enforcement Administration has joined the investigation into the death of actress Hayden Panettiere, the New York Times and ABC News reported, citing sources familiar with the matter.

Panettiere, 36, was found unresponsive Sunday at an apartment in Greenville, South Carolina. Medics, responding to a 911 call placed by her boyfriend and his brother, found her in cardiac arrest, according to authorities.

The one-time child star had spoken openly about navigating addiction and postpartum depression in her adult life, documenting those struggles as well as the painful loss of her brother in a memoir released this year.

While authorities have not addressed whether Panettiere overdosed Sunday, a possible overdose and CPR in progress are referenced in dispatch audio obtained from Broadcastify.com. Efforts to resuscitate her failed and she was pronounced dead at the scene at 2:32 p.m., the coroner’s office said.

 

Panettiere’s boyfriend, identified as Brian Hickerson, showed responding officers a bag of her medications, according to a police report, which was heavily redacted.

CNN has reached out to the DEA, Greenville Police and representatives for Panettiere for comment on drug enforcement agents joining the investigation.

No cause or manner of death has been determined, pending the results of additional testing. Toxicology tests, which are standard in many death investigations, could take weeks to complete.

An autopsy performed Monday revealed no signs of trauma that would have contributed to her death, the coroner’s office said.

CNN has reached out to Brian and his brother Zach for comment.

Panettiere’s sudden death sent waves of grief from Hollywood to Ukraine, where the father of their child mourned the beloved actress and activist who battled a host of struggles.

“Our family is going through a time of profound shock and grief,” Wladimir Klitschko, her ex-partner and a former world heavyweight boxing champion from Ukraine, posted Tuesday on X. “She built an incredible career through immense talent, while also facing the darker sides of a very demanding industry.”