The girl had been reported missing Monday. She was discovered by a passerby around 12:30 p.m. off of LaSalle Boulevard near the Mercier Bridge. It took ambulance workers three hours to get to climb down to where she was located and, once they reached her, they confirmed she was dead, Montreal police said. So far, investigators believe she may have accidentally slipped and fallen to her death, police said. Police say a coroner will perform an autopsy to determine the cause of death.