It happened on Sunday morning just after 10:30 a.m. on the 1800 block of East Wishart Street.
Neighbors told Action News 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. Officers intercepted their vehicle, at which time they transferred the girl to the police vehicle and rushed her to Saint Christopher's Hospital where she was admitted in critical condition.
The girl sustained serious injuries to both hands, as well as cuts to her chest, face, and burns to her eyes.
"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.'"
At a news conference on Monday, police said their investigation revealed that the girl's father purchased two illegal explosive devices the previous night from a man on the street.
According to police, the father exploded one of the devices and left the other device on the mantel inside the home.
On Sunday morning, the girl was left home alone, and that's when police say she picked up the explosive device. Police say it's unclear if the girl lit the device or if it detonated due to the handling of it.
Detective Tim Brooks of the Philadelphia Bomb Disposal Unit said devices similar the one that exploded in the girl's hands are illegally made, and by definition are improvised explosive devices, therefore they have no quality assurance.
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.
The girl remains in critical condition, but authorities say her injuries are not believed to be life-threatening.
Police say charges may be filed against the girl's father. Investigators are also looking for the man who sold the explosives.
Brooks said three young people were severely injured by illegal explosive devices in June alone. A 21-year-old man from Germantown who asked for his name not to be used said he lost four fingers when a device exploded in his hands on June 4th.
He found a bag on the street containing what he thought were fireworks. He warned others to learn from his mistake.
"It's not like a regular little firework you got but it looked just like it. So you really got to be careful what you're playing with because it looked just like everything else," said the victim.