The girl was struck just before 8 a.m. at the intersection of McFadden Avenue and Newhope Street near Fitz Intermediate School.
The child was transported to a hospital in critical condition. By Wednesday afternoon, officials said she was out of surgery and listed in stable condition.
The driver remained at large after fleeing the scene.
Grisell Ramirez witnessed the collision. She was driving through the same intersection and says she had to swerve suddenly to avoid the girl. But the driver in the lane next to and slightly behind her apparently didn't see the girl and struck her.
"He was behind but in the next lane to me. He didn't see her. And run over her. But he didn't stop either," Ramirez said.
"He slowed down. It looked like he was gonna pull over. Then the next street he put his right signal on. Never saw him after that."
The vehicle involved in the collision is described as possibly a blue Honda with damage to the passenger side windshield that was last seen heading eastbound on McFadden Avenue, according to the Santa Ana Police Department. Authorities released a surveillance camera image of the car being sought.
"Because of how distinct the vehicle is, it's easily identifiable," said Natalie Garcia with Santa Ana police. "We're asking anyone with information to please contact us."