However, officers say they are not releasing the girls' identity to the public at this time.
Investigators add, due to the ongoing investigation and the multiple jurisdictions involved, any other information is being withheld for now.
The girl was identified as a result of a pair of tip calls that came in early Wednesday morning from outside the Delaware Valley area.
Police sources say they are concerned about the mother's safety and do not believe she abandoned her child voluntarily.
The child, believed to be about 2 years old, was discovered in Newark by a stranger who heard her crying.
Division of Family Services spokesman Joseph Smack said the girl is now with a foster family.
Newark police released two video clips late Tuesday of the girl playing with toys after her rescue.
The discovery was made around 2:45 p.m. Sunday.
RELATED:CLICK HERE for a larger photo of the girl
Richard Sedlak from western Pennsylvania is a power company lineman who was passing through on the way to a job in Maryland. He stopped, intending to use the bathroom at a Shell gas station at 804 South College Avenue, near the University of Delaware. He got a key from the attendant and headed to the door, but heard crying from inside.
"He waited a few minutes, thinking there was a parent and child inside," said Lt. Brian Henry of the Newark Police. "But when the crying continued and nothing else happened he opened the door and found the child inside, alone."
Smack say they've received calls from all over the country from people who wanted to adopt the girl.
The Middlesex County Prosecutor's Office is now heading the investigation.
