The Drug Enforcement Administration has joined the investigation into actress Hayden Panettiere's death, working alongside South Carolina's Greenville Police Department and the local coroner's office. Panettiere, best known for her role as Claire Bennet on NBC's "Heroes" and her recurring appearances on "Nashville," died Sunday at age 36.

The DEA's involvement signals potential substance-related angles to the investigation, though authorities have not released an official cause of death. Panettiere had spoken publicly about her struggles with alcohol addiction in recent years. She entered rehab in 2014 and again in 2021, discussing her recovery journey candidly in interviews.

The actress, who began her career as a child actor on "Guiding Light" before becoming a household name through "Heroes," also voiced Kairi in the "Kingdom Hearts" video game franchise. Beyond acting, she became known for animal rights activism and was a Humane Society ambassador.

Panettiere's sudden death at a relatively young age has shocked the entertainment industry. Her representatives have not released additional statements pending the completion of the investigation. The coroner's office is conducting an autopsy to determine the cause of death, with results expected in coming weeks.

The involvement of multiple agencies including the DEA underscores the scope of the inquiry. Authorities are examining all circumstances surrounding her death at her Greenville home.