It happened at approximately 5:30 p.m. on the 200 block of Comly Street in the city's Crescentville neighborhood.
According to police sources, the 31-year-old mother had double-parked her blue Chevy Traverse in the street to unload groceries and had brought her 2-year-old daughter inside their home.
At some point, however, the toddler reportedly left the house and followed her mother back out to the street. The mother did not see that she wasn't inside.
That's when sources say the mother unintentionally struck the young girl.
The child was transported to Einstein Medical Center, where she was later pronounced dead.
Police sources say there will be no criminal charges, and it has been deemed a tragic accident.
Authorities have not yet released the girl's identity.