Joan Rivers

Joan Rivers

Joan Rivers' preliminary autopsy results have been deemed inconclusive.

The New York Medical Examiner's Office have completed a physical examination of the body of the 'Fashion Police' host, who died yesterday (04.09.14) after being placed in a medically-induced coma last week after she suffered a cardiac arrest during a routine operation on her vocal cords, but could not find a clear "cause and manner of death."

A source told gossip website TMZ.com that further tests will be carried out on the 81-year-old star's remains to determine exactly how she died, including toxicology testing.

The comedienne's medical team will also be interviewed about the throat procedure she was undergoing when she stopped breathing on August 28.

Joan's only daughter Melissa Rivers, 41, confirmed her death in a statement yesterday, saying: "It is with great sadness that I announce the death of my mother, Joan Rivers. She passed peacefully at 1:17pm surrounded by family and close friends. My son and I would like to thank the doctors, nurses, and staff of Mount Sinai Hospital for the amazing care they provided for my mother."

A private funeral is scheduled to take place on Sunday (07.09.14) at Temple Emanu-El in Manhattan.

The synagogue's director's office told E! News that the memorial is invitation-only and will not be open to the general public.