( CNN ) -- The cardiac arrest leading to Joan Rivers ' death happened as the comedian 's personal doctor began performing a biopsy on her vocal cords , a source close to the death investigation told CNN . A staff member at Manhattan 's Yorkville Endoscopy clinic told investigators that the doctor , who has not been publicly identified , took a selfie photo in the procedure room while Rivers was under anesthesia , the source said . Rivers , 81 , was at the clinic for a scheduled endoscopy by another doctor , gastroenterologist Dr. Lawrence Cohen . That procedure , intended to help diagnose her hoarse voice and sore throat , involved the insertion of a camera down her throat . After Cohen , the clinic 's medical director , finished his work , a biopsy was done on Rivers without her prior consent , according to the source . An ear , nose and throat specialist not certified by the clinic as required by law performed a biopsy on her vocal cords . The doctor is described by the source as Rivers ' personal ear-nose-throat physician . Clinic : Vocal-cord biopsy did not kill Joan Rivers . `` Even though you are a licensed physician , you still should have , if you will , the checks and balances to get your approval to practice in that particular place , '' said Dr. Arthur Caplan , a medical ethicist at New York University 's Langone Medical Center . Investigators believe that Rivers ' vocal cords began to swell during the allegedly unauthorized biopsy , cutting off the flow of oxygen to her lungs , which led to cardiac arrest on the morning of August 29 , the source said . Rivers , 81 , was rushed by paramedics from Yorkville Endoscopy to New York 's Mount Sinai Hospital a mile away , where she died a week later . Yorkville Endoscopy issued a statement last Thursday denying reports that any vocal cord biopsy has ever been done at the clinic , although federal privacy law prevented any patient information from being released . The day after the denial was issued , the clinic confirmed that Dr. Cohen `` is not currently performing procedures ... nor is he currently serving as medical director . '' The source said that at this time neither Cohen nor the ear , nose and throat doctor have been accused of wrongdoing by investigators . The clinic declined to respond to the source 's comments about a biopsy or a selfie , citing federal privacy law . Timeline emerges in Joan Rivers ' death . See more about the comedy business at CNN Comedy .
Rivers ' personal doctor who did the biopsy was not certified by the clinic , a source says . The doctor took a selfie while Rivers was under anesthesia , a clinic staffer tells reporters . Biopsy was done without Rivers ' prior knowledge , the source says . Rivers died a week after suffering cardiac arrest at the Manhattan clinic .