Emergency crews found the 22-year-old woman just before 4:30 a.m.
She was taken to Advocate Illinois Masonic Medical Center, where she was pronounced dead, according to CPD.
The Cook County Medical Examiner's Office ruled the death accidental, and said she died from electrocution from contact with the third rail.
SEE ALSO: Chicago police release photos of CTA Red Line robbery suspects
The Red, Brown and Purple lines stop at the Fullerton station in Lincoln Park on Chicago's North Side.
The incident caused delays on the Red and Brown lines.
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