Videotape of the medical procedure performed on Joan Rivers will help investigators determine what led to her tragic death, The National ENQUIRER has learned.

While the New York State Health Department probes the Aug. 28 incident at a Manhattan outpatient clinic, sources say there is at least one film of doctors working on the 81-year-old comedy legend.

Rivers had complained of hoarseness and underwent an endoscopy, in which doctors used a tiny camera to look down her throat and into her digestive system.

Top expert Dr. James Thomas, who did not treat Rivers, told The ENQUIRER that similar cameras can “record both still pictures and video.”

Another camera may have also recorded the tragic events, he said.

“The hospital operating rooms I work in have a room video so the front desk can see if the surgeon is working,” Dr. Thomas said.

The ENQUIRER has also learned a video surveillance camera is located inside the entrance of the Yorkville Endoscopy clinic.

Private investigator Dan Hanks, who is not involved in the probe, told The ENQUIRER: “It’s possible this video camera captured Joan walking into the facility. The same camera likely recorded her sadly leaving on a stretcher or gurney as she was fighting for her life.

“This film will also be valuable to investigators who are trying to determine exactly what went wrong.”

After the beloved comedienne was sedated, a tube was passed down her throat in an effort to examine her vocal cords. The showbiz veteran stopped breathing and suffered both respiratory and cardiac arrest.

Rivers was rushed by ambulance to New York’s Mount Sinai hospital where she died a week later on Sept. 4. She had never regained consciousness.

On Sept. 12, it was announced the gastroenterologist who performed the endoscopy on Rivers – Dr. Lawrence Cohen – stepped down as medical director of Yorkville Endoscopy.

A published report also claimed Dr. Cohen had allowed an ear, nose and throat specialist to participate in the procedure, though that physician was allegedly not authorized to practice medicine in the clinic.

Neither Dr. Cohen nor the ENT specialist Dr. Gwen Korovin have been accused of any wrongdoing — yet.