The fire broke out around 2:45 p.m. in the 200 block of South 18th Street in the Rittenhouse Square neighborhood.
Heavy fire could be seen on the roof of the 23-story Rittenhouse Claridge apartment building.
As Chopper 6 HD arrived at the scene, thick black smoke was billowing from the roof.
As the chopper moved to the other side of the building, flames could be seen leaping from the corner.
Firefighters quickly arrived and turned on the water. The black smoke turned white as the fire died down.
Within a few minutes, black scorch marks were the only evidence of the blaze.
No injuries have been reported.
Investigators say the fire erupted from a planter on the roof that was full of mulch. A worker saw the fire and tried to put it out with a garden hose, but was unsuccessful.
Only the roof flashing was damaged by the fire. There was no structural damage.
An investigation into this fire continues.
