NEW YORK (AP) — The New York City medical examiner says Joan Rivers died from low blood oxygen during a medical procedure.

The comedian, who was 81, died Sept. 4. She had been hospitalized since Aug. 28 when she went into cardiac arrest during a routine medical procedure at a doctor’s office to check out voice changes and reflux.

Medical examiner spokeswoman Julie Bolcer said Thursday that the cause was brain damage due to lack of oxygen. It is classified as a therapeutic complication, meaning that the death resulted from a predictable complication of surgery.

The New York state health department is investigating the circumstances.

Her daughter Melissa Rivers says in a statement that the family continued to be saddened by the tragic loss.