Yolanda Denise King, daughter of the late Rev. Martin Luther King, had just finished speaking at an event yesterday when she collapsed and later died. She was 51. AP library photo | May 2006

King died late Tuesday in Santa Monica, Calif., said Steve Klein, a spokesman for the King Center. The family did not know the cause of death but that relatives think it might have been a heart problem, he said.

"She was an actress, author, producer, advocate for peace and nonviolence, who was known and loved for her motivational and inspirational contributions to society," the King family said in a statement.

Former Mayor Andrew Young, a lieutenant of her father's who has remained close to the family, said Yolanda King had just spoken at an event for the American Heart Association. She was helping the association raise awareness, especially among blacks, about stroke.

Young said she was going to her brother Dexter's home when she collapsed in the doorway and "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.

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

One of her father's close aides in the civil rights movement, 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.

King also was an author 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.

She was the most visible and outspoken among the Kings' four children during this year's Martin Luther King Day in January, the first since her mother's death. At her father's former Atlanta church, Ebenezer Baptist, she performed a series of solo skits 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 to be a force for peace and love, and to use the King holiday each year 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."

The 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.

Survivors include her sister, the Rev. Bernice A. King and brothers Martin Luther King III and Dexter Scott King.