Joan Rivers had been sedated during the procedure examining the back of her throat
The comedian died on 4 September, aged 81, a week after she stopped breathing at the Yorkville Endoscopy centre.
A report released by the Department of Health cited multiple
errors, including failing to detect Rivers' deteriorating vital signs
during the procedure.
Negligence has not been alleged.
The New York medical examiner's office ruled Rivers died of
brain damage due to lack of oxygen during the procedure examining the
back of her throat and vocal cords
The death was classified as a "therapeutic complication", meaning it was a known risk.
The comic had been sedated with the anaesthetic propofol,
however the report said there there were inconsistencies recorded in its
dosage.
It added there was no record staff at the clinic weighed Rivers before administering the drug.
'Misconduct and mismanagement'
Hypoxia - brain damage caused by lack of oxygen - and cardiac
arrest are rare side effects of propofol, but patients usually sign a
waiver before surgery to confirm they understand the risks.
But the report said there were no records of medical consent for all the procedures performed.
Investigators said the clinic "failed to identify deteriorating vital signs and provide timely intervention" in Rivers' case.
They also noted a staff member took pictures of the comic
without her consent while she was under anaesthesia, in violation of the
clinic's mobile phone policy.
Rivers daughter Melissa said she was "outraged by the
misconduct and mismanagement" that occurred and wanted to ensure it does
not happen again with any other patient.
Her lawyers are investigating the circumstances surrounding her mother's death.
As a result of the state investigation, the Department of
Health and Human Services has given Yorkville Endoscopy until 7 January
to correct deficiencies to avoid losing accreditation to the
government's Medicare programme covering the elderly.
The clinic told NBC it had submitted a plan to officials
addressing all the issues raised. It added the physicians referenced in
the report no longer provided services there.