Authorities said it happened on the "El" train in West Philadelphia around noon on May 28.
The suspects confronted the victim then prevented her from getting off the train when it stopped, according to police. They stole her phone then blocked her exit again to prevent her from chasing them, the video shows.
Police believe the suspects are teenagers.
Anyone who can identify them is asked to call 215-686-8477 or submit a tip to the PPD website.
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