Mystery surrounds the death of Sister Sledge star Joni Sledge, the singer best-known for the seventies disco-era anthem We Are Family.
The 60-year-old was found unresponsive by a friend at her home in Phoenix, Arizona, on Friday.
No cause of death has been given for Sledge , who had not been ill at the time according to her publicist, Biff Warren.
Her death was announced on social media on Saturday – a week before the group were due to perform in Los Angeles.
“Numbness fell upon our family,” a statement released on Facebook read.
“We are saddened to inform you that our dear sister, mother, aunt, niece and cousin, Joni passed away yesterday.”
It added: “We miss her and hurt for her presence, her radiance, and the sincerity with which she loved and embraced life.
“Pray for us as we weep for the loss of our sister, mother, aunt, niece and cousin Joni Sledge.”
Sledge, who formed Sister Sledge with her three siblings in 1971, last performed with the band in October.
The singers along with Debbie, Kim and Kathy had struggled for years before finding success.
“The four of us had been in the music business for eight years, and we were frustrated,” she said last year.
“We were saying: ‘Well, maybe we should go to college and just become lawyers or something other than music because it really is tough.”
Only when they met Bernard Edwards and Nile Rodgers of the hit group Chic did they find fame.
Edwards and Rodgers wrote and produced their album “We Are Family,” and soon the women had their first major hit with their song “The Greatest Dancer,” which became a top 10 hit in May 1979.
Along with other songs Lost in Music, We are Family and a cover of the Motown classic My Guy, and the group went on to sell millions of records earning Grammy nominations.
The Sledge sisters came from a family of performers, including an actress mother, a Broadway star for a father and an opera singer for a grandmother.
They performed together from a young age, leading Sledge to say once “I can’t remember not singing”.
However, the four did not remain together throughout their careers.
Instead, the band became a trio after sister Kathy left the band in 1989.
They sang We Are Family for Pope Francis in 2015.
Sledge is survived by a son, Thaddeus, and her sisters Debbie, Kim and Kathy Sledge.