(CNN) -- The doctor who began a biopsy on Joan Rivers' vocal cords before she suffered cardiac arrest last month has been identified by clinic staffers as Dr. Gwen Korovin, a source close to the death investigation said.
Korovin is the same doctor who a clinic staff member told investigators snapped a selfie in the procedure room while Rivers was under anesthesia on August 29, the source said.
Rivers, 81, died a week after suffering cardiac arrest during an appointment at Manhattan's Yorkville Endoscopy clinic.
Rivers' throat doctor is well known for helping an impressive list of celebrities with voice trouble. The list of famous patients who have sung her praises include actors Hugh Jackman and Nathan Lane and singers Celine Dion, Lady Gaga and Ariana Grande.
CNN has been unable to reach Korovin despite multiple attempts over the past few days. A woman who answered CNN's call to her office Wednesday said the doctor would not comment on the disclosure of her name as Rivers' doctor.
The walls of Dr. Korovin's Manhattan medical office are covered with autograph photos, including from operatic tenor Luciano Pavarotti, Broadway star Barbara Cook and actress-singer Julie Andrews.
"I've always been fascinated by the human voice and music," Korovin, 55, is quoted telling the New York Daily News in a profile story last year.
Korovin accompanied Rivers to her appointment on August 28 for an endoscopy procedure intended to diagnose why the comedian was suffering a sore and hoarse throat, a source close to the death investigation told CNN.
Korovin was only authorized to observe while another doctor, gastroenterologist Dr. Lawrence Cohen, performed the procedure, the source said. After Cohen, the clinic's medical director, finished his work, Korovin began a biopsy on Rivers, according to the source.
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 was rushed by paramedics from Yorkville Endoscopy to New York's Mount Sinai Hospital a mile away, where she died a week later.
CNN's Lena Jakobsson contributed to this report.
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