Joan Rivers' Cause Of Death Unknown According To Medical Examiner

Comedy legend Joan Rivers' sudden death has caused much speculation. But the New York medical examiner explains that further tests are needed to rule a specific cause of death.

The Medical Examiners Office tells Fox411, "Following an examination, the cause and manner of death are pending further studies."

Rivers died Thursday at Mount Sinai Hospital in New York after she stopped breathing during a procedure at the Yorkville Endoscopy Center. The clinic is now under investigation after she went into cardiac arrest and eventually died at Sinai six days later.

"The state department of health is investigating the matter," a rep tells Fox 411. "It's full investigation of the matter ... Since it's an ongoing investigation I can't comment on what we're looking at."

The funeral for the sharp-tonged comedian will be held privately at Temple Emanu-El on Sunday.

The late star is survived by daughter Melissa Rivers, 46, and grandson Edgar Cooper Endicott, 13. Melissa confirmed in a statement Thursday that her mother had passed.

"It is with great sadness that I announce the death of my mother, Joan Rivers," she wrote. "She passed peacefully at 1:17 p.m. 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."

She not only leaves behind her loving daughter and grandson, but also a slew of celebrities who admired the strong comedic star. Kelly Osbourne who was on E! Fashion Police with Rivers took to twitter to say, "I love you with all my heart @Joan_Rivers my life will never be the same without you!" Bette Midler wrote, "Joan Rivers has died. What a sad ending to a brilliant and tragi-comic life; one of the bravest, and funniest of all."