The victim, identified as a 30-year-old white female from South Philadelphia, was struck by a train near the Lombard-South Station in Center City shortly after 5:00 a.m.
According to SEPTA, surveillance video from the station shows the victim entering the Lombard-South Station two hours after service ended for the day.
Then, at 2:19 a.m., cameras captured the victim inadvertently walking off the platform and into the track area where she made contact with the third rail.
It is unclear if the woman was electrocuted by the third rail or killed when she was struck by the train. The Medical Examiner will determine the victim's exact cause of death.
SEPTA says they have no plans to release the surveillance video.
Service was suspended for several hours between the Walnut-Locust and Snyder Stations while police and SEPTA officials conducted their investigation.
The victim's name has not been released.