ATLANTA (May 16) - Yolanda Denise King, daughter and eldest child of civil rights leader the Rev. Martin Luther King Jr., has died, said Steve Klein, a spokesman for the King Center.

King died late Tuesday in Santa Monica, Calif., at age 51.

Klein said the family did not know the cause of death but thinks it might have been a heart problem.

Andrew Young, a lieutenant of Martin Luther King Jr.'s during the civil rights movement who remained close to the family after the civil rights icon's death, said Yolanda King had just spoken at an event for the American Heart Association.

Last year, Yolanda King became a spokeswoman for the organization, and promoted a campaign to raise awareness, especially among blacks, about stroke.

"She was on the way to spend the night with Dexter," Young said, referring to her younger brother. "I understand she got to his house and came in and collapsed in the doorway. They were not able to revive her."

Born on Nov. 17, 1955, in Montgomery, Ala., King was just an infant when her home was bombed during the turbulent civil rights era. She was a young girl during his famous stay in the Birmingham, Ala., jail. She was 12 years old when Martin Luther King Jr. died.

"She lived with a lot of the trauma of our struggle," said the Rev. Jesse Jackson, an aide of Martin Luther King Jr. "The movement was in her DNA."

As an actress, she appeared in numerous films and even played Rosa Parks in the 1978 miniseries "King." She also appeared in "Ghosts of Mississippi."

The Rev. Joseph Lowery said Wednesday he was stunned and saddened by the news of King's death.

"Yolanda was lovely. She wore the mantle of princess, and she wore it with dignity and charm," Lowery said. "She was a warm and gentle person and was thoroughly committed to the movement and found her own means of expressing that commitment through drama."

King -- an actor, speaker and producer -- was the founder and head of Higher Ground Productions, billed as a "gateway for inner peace, unity and global transformation." On her company's Web site, King described her mission as encouraging personal growth and positive social change.

Young said King was really trying to live her own life.

"She didn't want to be a child of the movement, she wanted to be what God wanted her to be," Young said. "She could never escape being a child of the movement, though. She was really feeling that she didn't just want to be the daughter of Coretta and Martin King. That was her struggle."

King was also an author and advocate for peace and nonviolence, and held memberships in the Southern Christian Leadership Conference _ which her father co-founded in 1957 _ and the National Association for the Advancement of Colored People. Her death comes more than a year after the death of her mother, Coretta Scott King.

King understood well what her father was about, said U.S. Rep. John Lewis, D-Ga., who worked alongside Martin Luther King Jr. during the civil rights movement. Lewis said he last saw King at Easter Sunday services for New Birth Missionary Baptist Church, where King's sister, the Rev. Bernice King, preaches.

"She used her acting ability to dramatize the essence of the movement," Lewis said of Yolanda King in a telephone interview on Wednesday.

"She could motivate and inspire and tell the story. I heard her recite 'I Have A Dream' on several occasions. She made it real, made it part of her. I think her father would've been very, very proud of her," Lewis said.

Yolanda King is survived by her sister, the Rev. Bernice A. King; two brothers, Martin Luther King III and Dexter Scott King; and an extended family.

Arrangements would be announced later, the family said in a statement.

Yolanda King was the most visible and outspoken among the Kings' four children during activities honoring this year's Martin Luther King Day in January, the first since Coretta Scott King's death.

At her father's former Atlanta church, Ebenezer Baptist, she performed a series of one-actor skits on King Day this year that told stories including a girl's first ride on a desegregated bus and a college student's recollection of the 1963 desegregation of Birmingham, Ala.

She also urged the audience at Ebenezer to be a force for peace and love, and to use the King holiday each year in January to ask tough questions about their own beliefs on prejudice.

"We must keep reaching across the table and, in the tradition of Martin Luther King Jr. and Coretta Scott King, feed each other," King said.

When asked then by The Associated Press how she was dealing with the loss of her mother, King responded: "I connected with her spirit so strongly. I am in direct contact with her spirit, and that has given me so much peace and so much strength."

A flag at The King Center, which King's mother founded in 1968 and where she was a board member, was lowered to half-staff on Wednesday.

This is so saddening. She, like her father and mother, was a supporter for so many causes. She will be deeply missed by all of those she's touched and helped.

This is so saddening. She, like her father and mother, was a supporter for so many causes. She will be deeply missed by all of those she's touched and helped.

It's really disheartening.

Damn. 51 is too young for anyone to die. My prayers are with the family.