The actress was pronounced dead on Sunday at an apartment in South Carolina.
The Drug Enforcement Administration has joined the investigation into the sudden death of actress Hayden Panettiere, sources familiar with the matter told multiple outlets.
It was not immediately clear what role the DEA is playing in the investigation.
The development comes after the Greenville Police Department in South Carolina released a redacted incident report providing new details about the scene and the circumstances surrounding Panettiere's death.
Police said officers responded to an apartment on Easley Bridge Road on Sunday after receiving a call about an unresponsive person.
According to the report, EMS continued life-saving efforts "for an extended amount of time" before Panettiere was pronounced dead at 2:31 p.m. An officer wrote that there did not appear to be any obvious physical reason for her being unresponsive.
Panettiere's on-again, off-again boyfriend, Brian Hickerson, and his brother, Zack Hickerson, were present when she died, according to the report.
The report does not indicate whether drugs or alcohol played a role in Panettiere's death. However, Brian Hickerson reportedly showed police a "bag of medication Hayden is currently on."
The case remains under investigation with the Greenville County Coroner’s Office, and an autopsy was planned. No official cause or manner of death has been announced.
Before her death, Panettiere released her memoir, "This Is Me: A Reckoning," in which she detailed her experiences with child stardom, addiction and recovery, postpartum depression, trauma, domestic abuse, loss and the pressures of Hollywood.
