Broad Street is open to traffic after an anonymous call placed to 911 at 7:41 a.m. threatened that there was a bomb in a blue public mailbox at Broad and Cherry Streets.
Yellow hazard tape cordoned off the main thoroughfare between Race and Arch Streets from 8 a.m. to just after 10 a.m.
Nearby buildings were evacuated as officers from various districts responded to the scene.
The Bomb Disposal Unit, which deployed a robot, set off a controlled explosion about 50 feet from the mailbox .
Two engines from the city's Fire Department were also on location before the area was declared safe at 10:21 a.m.