Joan Rivers' death still a mystery as reports swirl about clinic

Joan Rivers: 1933-2014

A look back at the life of comedian Joan Rivers.

A shroud of mystery still surrounds Joan Rivers’ Sept. 4 death.

Rivers stopped breathing and went into cardiac arrest during a procedure at a New York City clinic on Aug. 28. She was then taken to Mount Sinai Hospital and placed on life support. Seven days later, she died.

That much we know.

What we don’t know, is exactly what happened at Yorkville Endoscopy that caused the 81-year-old’s health to rapidly take a turn for the worse.

A report on Wednesday seemed to place the blame on an unplanned biopsy that supposedly was done at the clinic. The New York Daily News, citing medical sources with knowledge of the case, published a story claiming a biopsy on Rivers' vocal cords was done by a doctor who arrived at Yorkville Endoscopy with her, and she was placed under general anesthesia at the time.

But the New York City clinic denies ever having performed a biopsy of the vocal cords at their facility. Furthermore, Yorkville Endoscopy insists Rivers could not have been under general anesthesia, either.

“General anesthesia has never been administered at Yorkville Endoscopy,” it said in a statement. “The type of sedation used at Yorkville Endoscopy is monitored anesthesia care. Our anesthesiologists utilize light to moderate sedation.”

The New York Times, on the other hand, paints a much different picture of the Upper East Side clinic. It reports a 911 call about Rivers was first place at 9:40 a.m. and by 9:50 a.m. 10 emergency medical workers were on the scene trying to help save the TV icon. By the time the emergency workers arrived, the clinic had administered medications and CPR and Rivers was hooked up to a defibrillator and a breathing tube had been inserted, the Times reports.

“The resuscitation efforts appear to be as good as one could hope for,” an official told The Times.

Meanwhile, the both State Health Department and the New York City Medical Examiner’s Office are still investigating the cause of Rivers’ death. The Medical Examiner’s Office stated on Friday that “further studies” were needed to determine why the comedian died.

The State Health Department has said it sent officials to check out Yorkville Endoscopy and that the clinic was under investigation.

Yorkville Endoscopy could not immediately be reached for comment. The Medical Examiner’s Office and the State Health Department did not return FOX411’s requests for updates on their investigations.

In her book, the sharp-tongued comedian joked that dying of natural causes was boring. "It's the grand finale, act three, the eleven o'clock number — make it count. If you're going to die, die interesting! Is there anything worse than a boring death? I think not."