Officers responded to the Fourth Avenue and Ninth Street station in Park Slope around 1:15 p.m. for reports of a robbery.
Police say two suspects opened the conductor's door on a northbound F train and punched the 51-year-old conductor in her face.
They also stole a set of keys she had on her.
The victim refused medical attention.
Police say one person is in custody, and charges are pending.
They are still searching for a second suspect
The investigation is ongoing.
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