The actress was hospitalized after her fiery car crash over the weekend.
The actress' rep tells ET, “At this time Anne is in extreme critical condition. She has a significant pulmonary injury requiring mechanical ventilation and burns that require surgical intervention."
The rep continues, “She is in a coma and has not regained consciousness since shortly after the accident."
ET has learned that by Monday evening, Heche had been moved to the Grossman Burn Center in West Hills.
Video captured by CBS Los Angeles showed the carnage left behind after Heche crashed her car into a home. Another video showed the blue Mini Cooper speeding down the street before crashing.
Per the LAPD, the vehicle became engulfed in flames and she was transported to a local hospital for medical treatment by an ambulance.
Meanwhile, the Los Angeles Fire Department said that the vehicle struck and came to rest well within a 738-square foot two-story home, causing structural compromise and erupting in heavy fire prior to LAFD's arrival.
The incident remains under investigation.
In a since-deleted episode of Heche's Better Together podcast, reportedly posted on Friday morning, hours before her crash, the actress claimed to have been drinking vodka "with wine chasers" after being "rocked" by a "very bad day."
However, in a statement to ET, podcast producer Ryan Tillotson said that the episode was, in fact, recorded earlier that week.
"The episode was recorded on the Tuesday before the episode was released, and has been removed due to inaccurate reporting. Any reports that she recorded that episode on the day of the accident are false," Tillotson said.
Two of Heche's exes -- actors Thomas Jane and James Tupper -- each spoke out following the accident.
Jane, who worked with Heche on his HBO show Hung, Jane released a statement to the Daily Mail, sharing, "While Anne and I are no longer an item, today's tragic news was devastating to me and to all who love her," he said. "My heart goes out to Anne and her two sons. As of right now Anne is stable and expected to pull through. My thoughts and prayers are with Anne, one of the true talents of her generation. Thank God no one else was hurt."
Tupper, who shares 12-year-old son Atlas with Heche, shared a throwback photo of his ex and their son on Instagram, which he captioned, "Thoughts and prayers for this lovely woman, actress and mother tonight anneheche 💔 we love you."
For more on the shocking accident, see the video below.