She was 32.
A 911 call was made at 8:00 AM from a home in Los Angeles that is listed as belonging to her husband, Simon Monjack, the Los Angeles City Fire Department tells TMZ.
We're told Murphy was taken to Cedars-Sinai Medical Center where she was pronounced dead on arrival. Her time of death was listed as 10:04 AM.
Murphy starred in such films as "Clueless," "8 Mile," and "Don't Say a Word." Murphy was reportedly fired from last film, "The Caller," after reports she was problematic on set.
UPDATE 3:11 PM ET -- Sources tell TMZ Brittany Murphy's mom discovered her unconscious in the shower. We're told when paramedics arrived, they quickly determined Murphy was in full cardiac arrest and immediately administered CPR. They continued CPR in route to Cedars-Sinai Medical Center -- several miles away -- and Murphy was unresponsive. She was pronounced dead at the hospital.
We're told the LA County Coroner's is picking up Murphy's body from Cedars later today and will launch a death investigation.
UPDATE 4:00 PM ET -- We're also told the LAPD has launched a death investigation.
UPDATE 4:07 PM ET -- A rep for Murphy tells TMZ, "In this time of sadness, the family thanks you for your love and support. It is their wish that you respect their privacy."
UPDATE 5:21 PM ET -- Two LAPD officers were just spotted going into Murphy's home.
UPDATE 5:34 PM ET -- A neighbor of Brittany's tells TMZ she saw Brittany getting taken out on a stretcher with paramedics performing CPR. The neighbor said Brittany "looked dead."
UPDATE 10:00 PM ET -- Through Brittany's rep, the family released a statement: "The sudden loss of our beloved Brittany is a terrible tragedy. She was our daughter, our wife, our love and a shining star. We ask you to respect our privacy at this time."