The incident happened around 2:30 a.m. Sunday as the woman was leaving the Lorimer street L train station in Williamsburg.
The man followed the victim as she walked up the stairs, then allegedly sexually assaulted her and stole her cell phone.
The suspect then fled the scene.
He is described as a Hispanic man in his 30s, standing approximately 5-foot-9 and weighing about 185 pounds.
Anyone with information in regards to this incident is asked to call Crime stoppers at 1-800-577-TIPS (8477).
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