The New York Medical Examiner's office completed its autopsy on comedienne Joan Rivers and was not able to determine a cause of death. According to the New York Daily News, a spokeswoman for the city medical examiner said that further studies will be conducted to determine the "cause and manner" of her death.

The medical examiner's office is also investigating the clinic where Rivers was having throat surgery when she suddenly stopped breathing. A source told TMZ that the medical examiner will conduct toxicology tests and will interview staff members who were present during Rivers procedure.

There are also reports that Rivers' family could file a lawsuit against Yorkville Endoscopy Center. The State Health Department has also launched its own investigation into the clinic but, so far, no foul play has been suspected.

Last week the "Fashion Police" cohost was rushed to the hospital after she went into cardiac and respiratory arrest while undergoing surgery on her vocal chords. On Wednesday, Rivers was taken off life support at Mount Sinai Hospital in New York City and died the following day, Thursday, Sept. 4. She was 81 years old. 

Rivers' daughter, Melissa Rivers, announced her mother's death in a statement on Facebook.

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

"Cooper and I have found ourselves humbled by the outpouring of love, support, and prayers we have received from around the world," the statement continued. "They have been heard and appreciated. My mother's greatest joy in life was to make people laugh. Although that is difficult to do right now, I know her final wish would be that we return to laughing soon."