Police released photos of two men wanted for questioning.
"This information came in through an anonymous tip received by the Philadelphia Police Department," said Capt. John Craig with Northwest Detectives. "The tip was two individuals were graffitiing the Falls Bridge on April 21 at approximately 10:35."
Crews with Philadelphia's Community Life Improvement Program, or CLIP, spent today painting over the vandalism.
The program now falls under Mayor Cherelle Parker's Office of Clean and Green Initiatives.
Executive Director of CLIP, Tom Conway, said his department is making graffiti removal a priority.
"Our big task is the highways. Graffiti-free, zero-tolerance zones on the highways. Anytime you see graffiti on the highways, you report to 311 and we'll have it cleaned up within 72 hours, weather permitting," said Conway.
Police called the two men persons of interest and said it is a cat and mouse game for investigators to try to catch those who tag buildings, bridges and other structures.
Graffiti is costly to taxpayers to clean up.
"The blight upon the city. It is an ugly thing to see and doesn't reflect on the city and what we're trying to do to make this a first-class city," said Capt. Craig.
Police ask anyone with information to contact Northwest Detectives or 215-686-TIPS.