Joan Rivers died from brain damage due to lack of oxygen, the New York City medical examiner ruled Thursday. The legendary comedian went into cardiac arrest while sedated during a throat operation to check for voice changes and acid reflux disease, according to Julie Bolcer, spokeswoman for the medical examiner’s office.

Rivers’ death is classified as a “therapeutic complication,” which means her death resulted from a predictable complication of a medical procedure, Bolcer said Thursday. The medical examiner's investigation is now complete, she said.

Rivers, 81, died Sept. 4 in New York, a week after being rushed to Mount Sinai Hospital for cardiac arrest during a routine medical procedure at a doctor’s office in the city. Rivers was kept on life support after she was put into a medically induced coma following the complication.

Rivers’ daughter, Melissa Rivers, is reportedly suing Dr. Gwen Korovin, who was performing the operation at Yorkville Endoscopy when Rivers went into cardiac arrest.

Melissa Rivers told the Associated Press the family has no comment on the ruling at this time. “My mother’s greatest joy in life was to make people laugh,” she said in a written statement shortly after her mother’s death. “Although that is difficult to do right now, I know her final wish would be that we return to laughing soon.”