Fire Commissioner Adam Theil said that about half of all on-duty firefighters were at the scene battling the blaze at a warehouse on the 3300 block of Stokley Avenue.
The fire, which started around 2 a.m., quickly grew so large that it could be seen from miles away. Flames could be seen shooting from the roof as part of the building collapsed.
Officials said one firefighter suffered non-life-threatening injuries and is being treated at the hospital. No other injuries were reported.
The city-block long building reportedly houses a paper company called Treco Fibematics. The opposite end of the building is said to be owned by Temple University and houses administrative offices.
"I open up my bedroom window (and) my curtains, and I was like, 'you've got to be joking,'" said Wanda Compton of the moment she saw the flames.
The fire burned until firefighters got control of the flames at around 11:30 a.m., as worried residents like Shreen Council looked on.
"I was actually out here from 2 o'clock this morning until 5 o'clock watching it burn and collapse," said Council.
Randall Kirkland roamed through the neighborhood as firefighters were in the final hours of battling the flames. The warehouse was his former workplace decades ago.
"I worked in that building about three or four years," he said. "We used to do work for the railroad trains, rail cars and stuff like that."
He says the building was sturdy and sound during the three years that he worked there.
"The floors are 10 inches thick," he said. "The building is very strong."
It is unclear at this time if the structure was occupied at the time of the blaze.
The building is located in an industrial park that is separated from the surrounding residential area by railroad tracks. No evacuations were needed.
Council stood on her front porch and cheered for some of those firefighters as they passed by, thanking them for stopping for flames.
"I already told them they were my superheroes forever and always for saving my home and saving our community as a whole," she said.
Officials said firefighters will remain at the scene dousing hotspots for some time.
Philadelphia's fire commissioner says the six-alarm fire is the biggest the city has seen in at least three years. Three-hundred firefighters and emergency response personnel helped to extinguish the fire.
The cause of the fire is unknown at this time.