The girl was struck on train tracks running along Third Street, north of Dundas Street, at about 4:30 p.m. Saturday, said police spokesman Const. Will Knelsen.
She was taken to hospital in critical condition and was later pronounced dead at about 8:30 p.m.
Knelsen couldn't say what exactly the girl was doing there or who she was with, citing the ongoing investigation, but he did say the coroner has ruled that the death was accidental.
Foul play is not suspected.