A surveillance image released by police is grainy, but it's a potential break that could lead to the suspect.
Both victims remain hospitalized, and area residents have expressed their concern.
"That's so sad," one neighbor said. "My heart goes out to their family."
The hit and run happened at the corner of busy Highland and Washington avenues in Bridgeport shortly before 9 p.m. Monday.
After hitting the two victims, the vehicle headed north on Washington Avenue, but not before losing an important piece of evidence.
The vehicle dropped the driver-side mirror, and it was found at the scene of the crash.
"We do have the mirror, and we're hoping that that will provide some valuable leads to us," Bridgeport police spokesman Bill Kaempffer said. "We would ask any auto body shops out there or any car parts stores, if someone comes in looking for a driver's side mirror from an SUV, let us know."
This is the second hit and run involving a young child in the last month in the city.
Corey Gordon, just 2 years old, was hit by a car on Capitol Avenue on May 7.
There are still no arrests in that case.
"It's crazy around here, every day, it's always something new," area resident Antonio Trowell said. "And now a little girl getting hit right here."
Bridgeport's police chief promised city residents a thorough investigation, but aimed a message squarely at the driver of the vehicle.
"The clock is ticking," he said. "If you panicked and fled the scene, we need to hear from you."