Cause of death: heart attack
Ellen Naomi Cohen (September 19, 1941 – July 29, 1974), known professionally as Cass Elliot, was an American singer. She was also known as "Mama Cass", a name she reportedly disliked. Elliot was a member of the singing group the Mamas & the Papas. After the group broke up, she released five solo albums. Elliot received the Grammy Award for Best Contemporary (R&R) Performance for "Monday, Monday" (1967). In 1998, she was posthumously inducted into the Rock and Roll Hall of Fame for her work with the Mamas & the Papas.
Source : Wikipedia