"We ask that you pray for our father and leader," the statement said.
The Cook County Medical Examiner said 74-year-old Wallace Mohammed was pronounced dead Tuesday. Mohammed went by both Warith Deen Mohammed and Wallace Muhammad. An autopsy was planned for Wednesday.
"Obviously, it's a great loss for the entire Muslim community," said Dawud Walid, executive director of the Council on American-Islamic Relations in Michigan, where Mohammed led a convention last month. "He was encouraging his followers to accept the best of their humanity and to extend the moral and ethical values of Islam to the general American public."
When Mohammed's father, Elijah Muhammad, died in 1975, his son was named leader of the Chicago-based Nation of Islam, which promoted self-reliance and black supremacy, a belief that mainstream Muslims consider heretical.
Mohammed quickly abandoned that teaching and led the Nation toward orthodox Islam, emphasizing the faith's message of racial tolerance. He had been a friend of Malcolm X, who abandoned the Nation to embrace mainstream Islam before he was assassinated in 1965.
Minister Louis Farrakhan, who broke with Mohammed over the move to orthodox Islam, separately revived the old Nation of Islam.
Farrakhan and Mohammed reconciled in 2000 through meetings and a joint public appearance at a Friday prayer in Chicago. Still, Mohammed remained critical of many Nation of Islam leaders.
"The time for those leaders who had that hate rhetoric has come and passed - and they know it," Mohammed said in an interview last year in Little Rock, Ark. "For the last 10 years or more, they've just been selling wolf tickets to the white race and having fun while they collect money and have fancy lifestyles."
The Nation of Islam didn't immediately return telephone messages seeking comment.
Born in 1933 in the Detroit area, Mohammed was the seventh of eight children. He was interested in Islam from an early age, said Lawrence Mamiya, a religion professor at Vassar College in Poughkeepsie, N.Y.
"He was a great African-American Muslim leader who opened up Islam to the wider American public," Mamiya said.
In 1990, Mohammed was the first Muslim to open the U.S. Senate with prayer.
"His intrinsic intelligence and high academic acumen made him wise, but his kind heart and charitable character is what made him so beloved," Rep. Andre Carson, D-Ind., who is Muslim, said in a statement Tuesday. "I extend my sympathies to his family and friends as they mourn his passing."
No one knows the size of Mohammed's movement, which was decentralized with many leaders and many entities, including The Mosque Cares. However, the number of his followers is believed to be in the tens of thousands.
The movement included not only mosques nationwide, but many business projects, which reflected the continued emphasis on black economic self-reliance that had been part of the Nation of Islam's mission.
The movement's decentralization makes it unclear who will succeed Mohammed.
Jimmy Jones, a Muslim chaplain and religion professor at Manhattanville College in Purchase, N.Y., joined Mohammed's movement in 1979, during the transition toward orthodox Islam.
"He asked the believers to stop reading and learning what his father had taught and start listening to him," Jones said after learning of Mohammed's death from a movement leader.
Mohammed changed his name several times from his birth name, Wallace Muhammad, to Warith Deen Muhammad and W.D. Mohammed. Jones said the renaming partly reflected the imam's struggle to maintain a triple identity: Muslim, African-American and American.
"He was trying to move a community that called itself an Islamic community closer to Islam without losing its roots and trying to situate itself in the context of American culture," Jones said.
Mohammed's businesses included importing clothing, developing skin care products and real estate development. Among the social service work he championed was promoting education, improving access to health care and supporting convicts after they were released from prison.
Associated Press writers Rachel Zoll in New York and Jeff Karoub in Detroit contributed to this report.