U.S. Customers and Border Protection officers made the discovery at the International and Bulk Mail Center in Jersey City.
Police are questioning Joshua Flecha in nearly 20 or more gropings of women, and believe he may be one of the men in six sketches of suspects posted around Brooklyn.
On Friday, the NYPD was canvassing Windsor Terrace, where another sex assault bumped the total to 20 in Brooklyn since March.
Martinez allegedly grabbed a woman from behind and groped her as she was walking near 36th Street and between Fourth and Fifth Avenues early Monday morning.
The NYPD released a sketch of the suspect who assaulted a 40-year-old woman in Springfield Gardens on Sunday.