Joan Rivers' cause of death needs ‘further studies,’ medical examiner says

NEW YORK – As her family prepares for her Sunday funeral, questions remain about comedy legend Joan Rivers' sudden death.

The New York City Medical Examiner’s Office tells FOX411 they were unable to determine Rivers’ cause of death after their initial examination.

“Following an examination, the cause and manner of death are pending further studies,” the official told us.

The Department of Health is also investigating Yorkville Endoscopy, the clinic that Rivers’ went to on Aug. 28 for a minor procedure. While at the clinic she stopped breathing and went into cardiac arrest. She was then rushed to Mount Sinai Hospital and was put on life support before she eventually died six days later on Thursday. She was 81.

Yorkville Endoscopy did not answer the phone on Friday.

“The state department of health is investigating the matter,” a rep told us. “It’s a full investigation of the matter… Since it’s an ongoing investigation I can’t comment on what we’re looking at.”

Rivers, who was known for her sharp-tongued comedy and red carpet zingers, is survived by her daughter Melissa and grandson Cooper.

"My mother's greatest joy in life was to make people laugh,” Melissa said in a statement. “Although that is difficult to do right now, I know her final wish would be that we return to laughing soon."