It happened on Sunday morning just after 10:30 a.m.
Neighbors told WPVI they heard an explosion and saw smoke and heard screams coming from the child's home.
One neighbor covered the child's hands and rushed her to the hospital with her distraught mother.
"It was like a loud boom, it was so loud, I heard it in the back room," said Judith Sierra who lives across the street. "There was smoke coming out of the house. Then the neighbor was pushing the door real hard to get to the little girl."
Margarita Artiaga, who also lives across the street said, "I see the little girl, blood all over her body missing two of her fingers. I said, 'Oh my god.'"
Philadelphia Police Special Victim's Unit is investigating.
Police officers were expected to serve a search warrant on the home to look for devices similar to the one that injured the girl.
There is no word yet as to if any other devices were found.
Police believe the girl found an explosive, possibly an M-80. These devices are considered inherently dangerous, as any bit of friction, heat or a slight bump can cause the device to detonate. M-80s, M-100s, M-250s are all considered illegal.
The ATF's website states an M-80, only 1.5 inches long, can damage fingers, hands and eyes.