A doctor who was not authorized to practice medicine at Yorkville Endoscopy in Manhattan was present in the clinic’s operating room where Joan Rivers underwent a throat procedure last month before suffering a cardiac arrest, according to a report from the New York Times. The doctor had reportedly examined the 81 year-old comedian's voice box twice after another doctor performed an endoscopy, where a tiny camera is used to look into the digestive system.

The ear, nose and throat, or E.N.T, specialist’s name was not known to other doctors at Yorkville, a person related to the matter told the Times, adding that the doctor was not authorized to work at that clinic. Under federal law, a hospital is required to review the credentials and qualifications of doctors before allowing them to perform procedures on patients inside their facility.

“In the final phase, they noticed her oxygen dropping quickly,” one of the people related to the matter, said, according to the Times. "They tried to stabilize her.” But, when the efforts to revive the actress failed, they called 911. Neither of the doctors is accused of any wrongdoing though the New York State Health Department is investigating Rivers’ death.

The Daily News had first reported about the presence of the E.N.T. doctor at Yorkville, and had added that the doctor had even performed a biopsy on her. However, Yorkville denied the claims Wednesday.

The E.N.T doctor, who was reportedly brought in by Rivers’ gastroenterologist Lawrence Cohen to check the comedian’s vocal cords, was identified only as an observer and not a doctor. Other workers in the clinic reportedly thought her to be a make-up artist who might attend to Rivers after the endoscopy. Cohen said, according to the Times, that acid reflux can bring changes to a person’s vocal cords.

Rivers died on Sept. 4 at Mount Sinai Hospital.