Actress Hayden Panettiere was found dead by a friend inside a South Carolina home on Sunday, according to law enforcement sources.
The friend called 911 at 1:51 p. m.
to report that Panettiere was unresponsive and in cardiac arrest at a residence in Greenville, SC.
It remains unclear whether her on-again, off-again boyfriend Brian Hickerson placed the call.
Police and EMS workers responded quickly, and paramedics attempted to resuscitate her using advanced cardiac life support, which includes CPR, medications, breathing tubes, and heart rhythm monitoring.
Despite chest compressions, she could not be revived and was pronounced dead at 2:32 p. m.
Authorities said there were no initial signs of foul play, and the circumstances did not appear suspicious.
The Greenville County coroner will perform an autopsy Monday to determine the cause and manner of death.
Panettiere began her career as a child star and was best known for her roles in 'Heroes' and 'Nashville.'
She also appeared in films such as 'Remember the Titans,' 'Raising Helen,' 'Ice Princess,' and 'Scream 4.'
She was 36.