Police vehicles from multiple municipalities lined the Bond Shopping Center at Lansdowne and State Road in Delaware County.
Upper Darby Police say officers were working to help people clear the area when "numerous" people refused repeated instructions to leave and began disrupting local businesses and others who were going home.
Authorities say officers inside and outside the event gave multiple warnings before making arrests. They did not specify how many arrests were made.
Action News obtained video from a woman who was nearby who was live-streaming the crowds of people and the responding officers trying to disperse them when you hear what sounded like gunshots.
Action News is working to confirm if those were indeed shots, but people started running.
Due to the size of the crowd, Upper Darby police asked for assistance from other municipalities. Pennsylvania State Police troopers were among those who responded.
RELATED: Looking for fireworks near you in the Philadelphia area? Check out this list
In New Jersey, two communities cancelled festivities due to security concerns.
In Mount Holly, public safety officials say there have been too many large events lately that have gotten out of control.
In addition, Gloucester Township Day -- a summer celebration typically held in June -- was cancelled for the second year in a row after large groups of juveniles got out of control.