Anne Heche remains on life support and under evaluation for organ donation after a car crash that led to her brain death, a representative for the actor says.
Earlier reports claimed doctors had turned off her life support.
Under current California law, death can be determined by the loss of all brain function and in accordance with accepted medical standards.
The 53-year-old was in a coma after her car burst into flames when it smashed into a house in West Los Angeles.
The news was confirmed by a family representative to US news outlet TMZ.
"We have lost a bright light, a kind and most joyful soul, a loving mother, and a loyal friend," the statement read.
"Anne will be deeply missed but she lives on through her beautiful sons, her iconic body of work, and her passionate advocacy. Her bravery for always standing in her truth, spreading her message of love and acceptance, will continue to have a lasting impact.”
Heche has two sons: Homer Laffoon, 20, with ex-husband Coley Laffoon and Atlas Tupper, 13, with her ex James Tupper.
"My brother Atlas and I lost our mom," Homer, 20, said in a statement to PEOPLE.
"After six days of almost unbelievable emotional swings, I am left with a deep, wordless sadness. Hopefully, my mom is free from pain and beginning to explore what I like to imagine as her eternal freedom."
He continued: "Over those six days, thousands of friends, family, and fans made their hearts known to me.
"I am grateful for their love, as I am for the support of my dad, Coley, and my stepmom, Alexi, who continue to be my rock during this time. Rest in peace, Mom. I love you."
Tupper also paid tribute to the actress, posting a photo on Instagram simply captioned, "love you forever".
Heche was reported "brain dead" on Friday afternoon by TMZ, which under California law is the definition of death.
It was announced earlier in the day that Heche would be taken off of life support.
Earlier on Thursday, local time, police said they were investigating Heche for driving under the influence.
Detectives with a search warrant took a sample of her blood and found narcotics in her system, LAPD spokesperson Jeff Lee said.
Toxicology tests — which can take weeks to complete — must be performed to identify the drugs more clearly and to differentiate them from any medication she may have been given for treatment at the hospital.
Evidence is still being gathered from the crash, police said, and they would present a case to prosecutors if it is warranted when the investigation is complete.
A representative for Heche declined to comment on the investigation.
Hollywood remembers 'profound talent', 'beautiful friend'
A native of Ohio, Heche first came to prominence on the NBC soap opera Another World from 1987 to 1991.
In 1997, she played opposite Johnny Depp in Donnie Brasco, and Tommy Lee Jones in Volcano and was part of the ensemble cast in the original I Know What You Did Last Summer.
The following year, she starred with Harrison Ford in Six Days, Seven Nights and appeared with Vince Vaughn and Joaquin Phoenix in Return to Paradise.
Her relationship with Ellen DeGeneres from 1997 to 2000 heightened her fame and brought immense public scrutiny.
DeGeneres was among many of Heche's Hollywood friends to pay tribute to the actress.
"This is a sad day," she wrote. "I'm sending Anne's children, family and friends all of my love."
Comedian Ed Helms wrote that he was "heartbroken" by the news.
"A truly epic, vibrant spirit and a profound talent. Sending tremendous love and support to her family."
Nancy Davis, a friend, wrote on Instagram: “Heaven has a new Angel. My loving, kind, fun, endearing and beautiful friend @anneheche went to heaven. I will miss her terribly and cherish all the beautiful memories we have shared."
Organ donation 'long been her choice', family says
Heche remained on life support so that the non-profit organisation OneLegacy could determine if she could be a donor, spokeswoman Holly Baird said in a statement.
The process, which involves assessing which organs are viable and finding an appropriate recipient, could take up to several days, Ms Baird told Associated Press.
In the US, most organ transplants are done after the donor has been declared brain-dead.
"It has long been her choice to donate her organs," said a statement from her family and friends issued on Thursday.
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