The collapse was reported at 9:22 a.m. Thursday at a building in the 400 block of Walnut Street.
The scaffold was hanging off the side of the building and suspended 25-30 feet above an adjacent roof when the incident occurred.
Action News is told a line supporting part of the scaffold snapped, causing it to buckle.
Two workers were injured.
A 23-year-old man suffered cuts to his left arm and right leg, and a 41 year-old man suffered cuts to his face and right arm.
Both were taken to Thomas Jefferson University Hospital. There was no immediate word on either man's condition.
Police closed the 400 block of Walnut Street as inspectors from the Philadelphia Department of Licenses and Inspections check the property for possible structural damage.
An investigation into the incident continues.
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OLD CITY, PHILADELPHIA (WTXF) - A scaffolding accident has two window washers in the hospital with minor injuries, and a block of Walnut Street in Old City closed.
Philadelphia police say the scaffold line at 4th and Walnut streets snapped approximately 25 to 30 feet.
The accident happened on the west side of the building at about 9:20 a.m. Thursday.
Authorities say the victims were knocked off the scaffolding, but luckily they were strapped on.
A 23-year-old man suffered cuts to his left arm and right leg, and a 41- year-old man suffered cuts to his face and right arm. Police say their conditions are not known at this time.
The 400 block of Walnut Street, from 4th to 5th streets, is closed.
Both OSHA and L&I have been notified to investigate.