Hayden Panettiere investigation now cross-country and focused on drugs, sources say

The investigation into the death of actress Hayden Panettiere is now a cross-country investigation in both Los Angeles and South Carolina, sources told ABC News.

The investigation is focusing in on what drugs may have played a role in her death, and where the drugs came from, the sources say.

Panettiere, known for her roles in "Heroes," "Nashville" and "Ice Princess," died on Aug. 16 after she was found unresponsive and in cardiac arrest at a residence in Greenville, South Carolina. First responders attempted to resuscitate her, but she was pronounced dead at the scene.

This is a developing story. Please check back for updates.