Actress Misty Upham appeared in August: Osage County and Django Unchained
A family spokeswoman has confirmed that a body found in a ravine near Seattle is 32-year-old actress Misty Upham.
Upham, known for roles in August: Osage County and Django Unchained, had been missing since 6 October.
Her body was found following a search of the area by friends and family. Her father, Charles Upham, confirmed her identity to the authorities.
The Native American actress was understood to have suffered from bipolar disorder.
Police Commander Steve Stocker said there was presently no evidence or information "to believe there is foul play."
At the time of her disappearance, her father expressed concern that the actress was off her medication and may have been suicidal.
However, film-maker Tracy Rector - a long-time friend and spokesperson for the family, said: "The family has stated that, after seeing the body, they still do not feel that Misty Upham committed suicide."
The body was found by a family member during a search of the area on Thursday. A purse with identification belonging to Upham was reportedly found at the scene.
Upham cropped her hair and gained a significant amount of weight to play Lila in Frozen River
Ms Rector suggested there was hostility between local police and the Native American community who live on the Muckleshoot reservation, where Upham had been staying.
"The family wants everyone to know that the Auburn police did not help with this situation at all. They refused to help. When she disappeared on Oct. 5, the family knew something was seriously wrong - it was out of character for her to be gone so long without being in touch - and they repeatedly went to the police, who insisted there was no cause for concern," she told the Hollywood Reporter.
Actress Juliette Lewis tweeted that Upham "spoke out a lot against injustices within the Native community. And had known enemies. Police must do an investigation".
Lewis later tweeted: "I can't sleep. Too much darkness. I feel so sad about Misty. I know she has more to say. And about how she died."
Upham, who played the housekeeper in the 2013 film August: Osage County with Meryl Streep, bemoaned the fact that, as a Native American, she was typically cast as "a maid, or a prisoner".
She once described herself as "painfully shy".
"When I'm in front of the camera, or talking to people as an actress, and not as myself, it's like I become another person. Somehow possessed with somebody who is worth talking to. Because at home people could care less about what I have to say," she said.
"So, so sad to hear this news — all our thoughts are with her family and with her beautiful spirit," Streep commented to the Hollywood Reporter, on learning of Upham's death.
Upham was nominated for an Independent Spirit Award for her supporting role as new mum Lila in the 2008 film Frozen River, in which she co-starred with the Oscar-nominated actress Melissa Leo, who called her death "such a loss.".
Animal charity Peta said: "The world will be a colder place without Misty's warm heart, and she will be sorely missed at PETA. She was extremely kind and cared deeply about animals; constantly calling for protection for the bears suffering in roadside zoos on tribal land, a call we will carry forward in her honour."
According to her family, Upham moved to the Seattle area to help care for Mr Upham, who had suffered a stroke. She was reportedly staying on the Muckleshoot reservation, and was last seen walking from an apartment south of Seattle.