A marked NYPD police car responding to a crime scene struck a teen girl in the Bronx early Saturday morning, cops said.

“The cop car was going north on Grand Concourse and had just given someone a ticket when it sped off through a red light and hit the girl in the crosswalk,” said witness Charles Simpson, 20.

Police said their sirens and lights were on when they took off to respond to a stabbing, but would not immediately provide a location or details of the nearby assault.

The unidentified 13-year-old girl was hit on Grand Concourse at East 170th Street about 12:07 a.m. and was taken to Jacobi Hospital in serious condition, a FDNY spokesman said.

Police Saturday morning said the teen is stable.

“She was trying to run across [the street] and then she got hit. The light was still blinking,” said Caroline Tejada, 20.

“Make a fist with your hand and punch a bag of potato chips. That’s what [the collision] sounded like,” said Shawn Thompson, 32.

Witnesses said the teen looked like she was severely injured by the crash.

“She was mangled. She was all twisted up. She was bleeding from the mouth and neck,” said Erica, who witnessed the crash.

“She looked like a human pretzel,” said another witness.