Messages left for Murphy's manager, agent and publicist weren't immediately returned.
Neighbor Clare Staples said she saw firefighters working to resuscitate the actress yesterday morning. She said Murphy was on a stretcher and "looked as though she was dead at the scene."
Murphy's husband, wearing pajama bottoms and no shoes, appeared "dazed" as firefighters tried to save her, Staples said.
"It's just tragic," she said.
TMZ.com first reported Murphy's death yesterday morning.
Murphy's father, Angelo Bertolotti, said he learned of her death from his son, the actress' brother, and was stunned.
"She was just an absolute doll since she was born," Bertolotti said from his Branford, Fla., home. "Her personality was always outward. Everybody loved her - people that made movies with her, people on a cruise - they all loved her. She was just a regular gal."
He said he hadn't heard much about the circumstances of Murphy's death. Bertolotti divorced her mother when Murphy was young and hadn't seen Murphy in the past few years.
"She was just talented," he said. "And I loved her very much."
Bertolotti was in the mob and served prison time on federal drug charges.
Born Nov. 10, 1977, in Atlanta, Murphy grew up in New Jersey and later moved with her mother to Los Angeles to pursue acting.
Her career started in the early 1990s with small roles in television series, commercials and movies. She is best known for parts in "Girl, Interrupted," "Clueless" and "8 Mile."
Her on-screen roles declined in recent years, but Murphy's voice gave life to numerous animated characters, including Luanne Platter on more than 200 episodes of Fox's "King of the Hill" and Gloria the penguin in the 2006 feature "Happy Feet."
She is due to appear in Sylvester Stallone's upcoming film, "The Expendables," set for release next year.
Her role in "8 Mile" led to more recognition, Murphy said in 2003. "That changed a lot," she said. "That was the difference between people knowing my first and last name as opposed to not."
Murphy credited her mother, Sharon, with being a key to her success.
"When I asked my mom to move to California, she sold everything and moved out here for me," Murphy said. "I was really grateful to have grown up in an environment that was conducive to creating and didn't stifle any of that. She always believed in me."
She dated Ashton Kutcher, who co-starred with Murphy in 2003's romantic comedy "Just Married."
Kutcher sent a message on Twitter yesterday morning about Murphy's death: "2day the world lost a little piece of sunshine," Kutcher wrote. "My deepest condolences go out 2 Brittany's family, her husband, & her amazing mother Sharon."