The fire occurred at the university hospital in Tokyo on April 15. The patient, in her 30s, was undergoing an operation which involved applying a laser to her cervix, the lower part of the uterus.
The laser is believed to have been ignited by the gas she passed. The fire burnt much of her body, including her waist and legs, the report said.
"When the patient's intestinal gas leaked into the space of the operation (room), it ignited with the irradiation of the laser, and the burning spread, eventually reaching the surgical drape and causing the fire," the report said.