Six days after the accident in which Anne Heche's car crashed into a Los Angeles apartment building, the actress was pronounced brain dead on Thursday.
"Her brain has been damaged by lack of oxygen and she remains in a coma.
She is unlikely to survive," said her spokeswoman.
On August 5, Heche drove into a bungalow in the Mar Vista district at excessive speed.
Almost 60 emergency services tried for almost an hour to free the 53-year-old Heche from the car and to extinguish the flames in the house that had caught fire.
After being rescued from the burning car, Heche had fought back violently before she lost consciousness.
As reported by American media, she is said to have consumed cocaine and fentanyl before the accident.
The actress, best known for films like "I Know What You Did Last Summer" and her romance with presenter Ellen DeGeneres, was said to have a mental illness.
After separating from actor James Tupper four years ago, the mother of two sons mostly lived alone.
According to her rep, Heche is being kept alive artificially for the time being to investigate whether her organs can be donated in accordance with the actress' request.