Officials have cordoned off an area by 18th and Chestnut streets after discovering a bag of money with an exploded dye in a nearby alleyway.
A man robbed the M&T Bank located on the 100 block of South 18th Street in Rittenhouse Square using pepper spray around 2:30 p.m., according to police.
The suspect was wearing a black baseball cap, a ski mask and white cargo pants, according to authorities.
Investigators said he was last seen heading eastbound towards 17th Street.
Police said they recovered a substantial amount of money on the 1700 block of Stock Exchange.
Stay with NBC10 for more on this developing story.