Now, a surveillance image has been released of the suspect.
Investigators say the man began groping a 13-year-old girl on a Bronx-bound No. 4 train at the 125th Street station just before 6 p.m. on March 26.
When the girl got off the train at 161st Street, the man followed her before fleeing the station.
There were no reported injuries.
The suspect is described as a Hispanic male between the ages of 20 and 40, last seen wearing a black coat and carrying a black duffle bag.
Anyone with information in regards to this forcible touching is asked to call the NYPD's Crime Stoppers Hotline at 800-577-TIPS.
