The investigation into Joan Rivers's death is far from over — but there's certainly movement in the ranks.

Dr. Lawrence Cohen, the medical director at Yorkville Endoscopy, where Joan Rivers was having her procedure and went into cardiac arrest, was asked by the board to step down from his post and accepted, The Insider With Yahoo confirmed on Friday.

"Dr. Cohen is not currently performing procedures at Yorkville Endoscopy; nor is he currently serving as medical director," a spokesperson for Yorkville Endoscopy said.

New details about an unauthorized doctor being present for the actress's medical procedure emerged late Thursday that led to Dr. Cohen's dismissal.

The New York Times reported that an ear, nose, and throat specialist was in the operating room at Yorkville Endoscopy in Manhattan on Aug. 28 when the comedian had her upper endoscopy despite the physician not being allowed to practice medicine in the clinic.

The unidentified E.N.T. specialist was brought in by Rivers's gastroenterologist, Dr. Cohen, and was identified as an observer, not a doctor, so clinic personnel assumed it was Rivers's makeup artist. However, the specialist examined Rivers's voice box before and after the gastroenterologist performed the routine procedure, during which a tiny camera was used to look down the throat into her digestive system as Rivers had been complaining of hoarseness and a sore throat.

[Related: Liza Minnelli: I Missed Joan Rivers's Funeral Because I Have a Broken Back]

The problem is that specialist was not cleared to work at the clinic, which must review and approve the credentials of every physician prior to allowing them to participate in procedures.

The report also has details about what went wrong during Rivers's procedure. Just as it was wrapping up, medical personnel realized that the Fashion Police host's oxygen level was crashing, a source said. It's unclear what led to that — whether it was a complication of the procedure or a result of the anesthetic she was given, which the person said was the powerful sedative Propofol.

The clinic called 911 and despite attempts to revive her at that facility, by paramedics transporting her to the hospital, and later at Mount Sinai Hospital, Rivers never regained consciousness. She died on Sept. 4 after being removed from life support.

[Related: 'Who Are You Wearing?': How Joan Rivers Reinvented Herself as a Fashion Icon]

The newspaper also states that Rivers went to the clinic for treatment "to avoid the publicity a hospital visit could bring." And a spokesperson for Yorkville Endoscopy, which opened in 2013, said their facility has the same level of lifesaving devices as any hospital emergency room or operating room.

As previously reported, both the New York Police Department and New York Health Department have been investigating the circumstances surrounding Rivers's death. Initial results of her autopsy were inconclusive, with the Medical Examiner's Office unable to find a clear "cause and manner of death."

[Related: Investigations, Memorials, Controversy: The Latest on Joan Rivers]

A funeral for Rivers was held Sunday at Temple Emanu-El in Manhattan. Her daughter, Melissa, made sure her mother's final wishes were honored and it was a star-studded event with celebrities from Hugh Jackman to Howard Stern participating. Rivers was cremated and a source told The Insider With Yahoo that the family is still deciding whether a portion of her ashes will be interred at Forest Lawn Cemetery in Los Angeles. On Thursday, Melissa and her son Cooper began the Jewish tradition of sitting shiva at their L.A. home.

(Originally published on Sept. 12, 2014, at 5:01 a.m. PT)