Rivers died at 81 Sept. 4 after spending a week at Mount Sinai Hospital in New York City on life support.
Dr. Lawrence Cohen, the clinic's former medical director and gastroenterologist who performed the endoscopy on Rivers, “is not currently performing procedures at Yorkville Endoscopy; nor is he currently serving as medical director,” the clinic said in a statement to ABC News.
The clinic gave no reason for Cohen's freeze at the clinic.
But the source said Cohen was asked to step down because he allowed a specialist unaffiliated with Yorkville Endoscopy to examine Rivers even though that doctor was not authorized to practice in the clinic.
A representative for Yorkville Endoscopy said, “HIPAA laws prevent us from disclosing any information about patients.”
The doctor has not responded to ABC News’ request for comment.
On the day of Rivers' cardiac arrest -- Aug. 28 -- the comedian was undergoing what close friend Deborah Norville described as "a diagnostic procedure ... [to] see why her voice had gotten raspy."
The call that day to 911 from Yorkville Endoscopy reportedly came at 9:39 a.m. and by 9:46 a.m., paramedics and other first responders were on scene. Rivers arrived at Mount Sinai Hospital at 10:08 a.m. She was reportedly already on life support and her condition at the time was near death. The legend died one week later when her daughter released a statement, saying, "It is with great sadness that I announce the death of my mother, Joan Rivers."