"We Are Family" singer and Sister Sledge star Joni Sledge has died at the age of 60.

Sledge, who co-formed the group alongside her three sisters in 1971, was found unresponsive at her home in Phoenix, Arizona on Saturday.

Her cause of death is yet to be determined, according to a statement from the band's publicist.

Philadelphia-born Sledge fronted the pop group with siblings Debbie, Kim and Kathy and sang on 1979 disco anthem "We Are Family."

While the song went on to reach No. 2 on the Billboard Hot 100 and attain international fame, the band was also known for "He's the Greatest Dancer", "Lost in the Music" and a cover of Motown classic "My Guy".

In a Facebook statement released on Sister Sledge's page, the group described how numbness "fell upon our family" at the news of Joni's death.

"We are saddened to inform you that our dear sister, mother, aunt, niece and cousin, Joni passed away yesterday," the statement said.

It added: "We miss her and hurt for her presence, her radiance, and the sincerity with which she loved & embraced life."