It is reported that a call went out to 911 from Murphy's Los Angeles home at 8 a.m. Attempts to revive her were not successful. A spokesperson for Cedars Sinai Medical Center confirmed to PEOPLE that Murphy died at the facility Sunday at 10:04 a.m.
The actress's rep, Nicole Perna, said in a statement Sunday afternoon, "In this time of sadness, the family thanks you for your love and support. It is their wish that you respect their privacy."
In addition to The White Hotel and Clueless, the Atlanta-born Murphy costarred in 8 Mile with Eminem, and Girl, Interrupted, with Angelina Jolie. Her first Hollywood job, at age 14, was as the star of the series Drexel's Class.
In May of 2007, she married her White Hotel director, Simon Monjack.
Before meeting the British writer-director, Murphy had been engaged twice. She split with best-boy grip Joe Macaluso in August 2006, and ended her engagement to Jeff Kwatinetz, CEO of the Hollywood talent agency The Firm, in 2004.
She previously dated Ashton Kutcher, her costar in 2003's Just Married.
On Sunday Kutcher Tweeted, "see you on the other side kid ... 2day the world lost a little piece of sunshine. My deepest condolences go out 2 Brittany’s family, her husband, & her amazing mother Sharon."
Music Career, TooIn addition to acting, Murphy also teamed with DJ Paul Oakenfold to release a single "Faster Kill Pussycat," which became a club hit and reached No. 1 on Billboard's Hot Dance Club Play chart.
Last month, she was reportedly fired from a movie she was working on in Puerto Rico, prompting her rep to tell news outlets, "She was not nor has she ever been fired from any job big or small ... [due] to creative differences Ms. Murphy and the production mutually parted ways."
Earlier this year, when stories circulated that the couple's marriage was in trouble, Murphy's husband told PEOPLE, "All these ridiculous people came out and said all this nonsense when we got married, [but] thank god we had the substance and the history within that to [say], 'Yeah, whatever!' "
He added, "We still don't understand what happened. It's made us laugh, it's made us cry, but it's made us stronger."
With reporting by CHAMP CLARK and JULIE JORDAN