"There was no explosion, there was no sticks of dynamite," said Chief Inspector Michael Cram.
The incident happened around 5:10 p.m. Tuesday at the Fresh Grocer located on the 5300 block of Chew Avenue in the city's Germantown section.
Police say security called to report three teens, roughly 16 to 19 years old, wearing all black clothing, trying to light some kind of fireworks.
But once bomb squad units arrived they found no evidence of explosives.
"When confronted, the teens left and they left what amounted to be a package of sparklers," Cram said.
"They do sell fireworks in that particular store, they did hear some popping, but there was no explosion, they think it might have been poppers."
The commotion was enough to concern shoppers inside the store, who say teens need a better outlet.
Police have not said how many people were inside the business at the time of the incident.
No physical injuries were reported.
Anyone with information is asked to call police at 215-686-TIPS.
Police originally stated that the teens were trying to light dynamite, but they later stated that was not true.