Sacheen Littlefather's sisters say she was not Native American. The actress had disputed similar claims before.

In 1973, actress Sacheen Littlefeather stepped on stage at the Oscars on behalf of Marlon Brando, identifying herself as a member of the Apache tribe and turning down his award because of the way Native Americans were treated in the U.S. Now, her two sisters are saying she lied — their family is not Native American.

Littlefeather, who died earlier this month at age 75, was active in the Native American Bay Area community. During her speech at the Oscars, she said she was president of the National Native American Affirmative Image Committee. In an interview published in a San Francisco Chronicle opinion column over the weekend, her biological sisters, Rosalind Cruz and Trudy Orlandi, said Littlefeather did not tell the truth that night.

"It's a lie," Orlandi told activist and writer Jacqueline Keeler in the exclusive interview. "My father was who he was. His family came from Mexico. And my dad was born in Oxnard," a city near Los Angeles. 

Littlefeather said she was part White Mountain Apache and part Yaqui, two tribes located in Arizona. 

"It is a fraud," her other sister said. "It's disgusting to the heritage of the tribal people. And it's just … insulting to my parents."

During her Oscars speech, Littlefeather said Brando was turning down his award because of the treatment of American Indians by the film and TV industry as well as protests at Wounded Knee in South Dakota at the time.

She was met with harsh criticism, and she said actor John Wayne even physically threatened her, attempting to take her off stage, before security guards apprehended him. 

Following the speech, Littlefeather's Native American heritage was also questioned. 

The homepage of Littlefeather's website addresses these claims, disputing film critic Roger Ebert, whom she said incorrectly called her a "Mexican actress." 

"Contrary to misinformation which has been published on the internet, Sacheen Littlefeather is indeed of true Native American Indian descent," the site reads. "Sacheen was born Marie Cruz in Salinas, California. Her mother is French-German-Dutch, and her father was from the White Mountain Apache and Yaqui tribes from Arizona. "

While "Cruz" is her father's recognized tribe name, the site says, Sacheen took the name "Sacheen Littlefeather" after high school to reflect her heritage. "She is not a 'Mexican actress' as Roger Ebert incorrectly reported." 

Ebert wrote a blog post about Brando in 2004 that the actor "will always be remembered for refusing to attend the Oscar ceremony for 'The Godfather' and sending a woman named Sacheen Littlefeather to protest discrimination against Native Americans."

"That Littlefeather was later identified as Maria Cruz, an actress who was not an Indian, only compounded his notoriety. [See clarification below on Ms. Littlefeather.]," Ebert's post continued. At the bottom of the post, Ebert added a 2005 letter from an attorney representing Littlefeather requesting a clarification that reiterated similar claims as her website, including that "Sacheen Cruz Littlefeather is a natural native american indian." The letter also claims Littlefeather was Yaqui and White Mountain Apache, her married name was Cruz, and that "Sacheen Littlefeather" was a stage name she adopted before graduating high school. 

More than 49 years after she made the Oscars speech, the Academy of Motion Pictures and Sciences, which holds the Oscars, also known as the Academy Awards, announced that they had delivered an apology to Littlefeather for the mistreatment she received. Roughly two months later, Littlefeather died. 

CBS News has reached out to the administrator of Sacheen Littlefeather's website about her sisters' claims and is awaiting response. 

In two separate interviews, Orlandi and Cruz said their family has Spanish heritage and they have never claimed to be Native American. The sisters approached Keeler because she had been compiling a public list of what she calls "Pretendians" — non-Native people who are suspected to be lying about their Native American identities.

The journalist says through research she found no documents from her father's extended family linking them to any Native American nations in the U.S.

Family records for events like marriage and baptisms date back to 1850 in Mexico. The records don't place either side of her father's family near White Mountain Apache or Yaqui communities, but she found the family lived in a village that is now part of Mexico City. 

Littlefield's relatives identified themselves as White, Caucasian and Mexican on legal documents, as did their spouses. CBS News has reached out to both the White Mountain Apache and Yaqui tribes and is awaiting response. Officials for the White Mountain Apache tribe told Keeler there was no record of Littlefeather or her family members being enrolled.

Keeler says the first records that identify Littlefeather as Native American are from the 1960s — news outlets in the Bay Area reporting on her modeling career when she was a college student. 

For the column, Keeler, who founded a group that advocates for an end to mascots based on racial groups and opposes cultural appropriation, also spoke to others who disputed claims Littlefeather made throughout her life. CBS News has reached out to Keeler for a statement and is awaiting response.

Orlandi said some of Littlefeather's claims "infuriate" her. CBS News has not been able to reach either sister with a request for comment.