A man who attacked a woman waiting for a bus Sunday night left his pants at the scene and ran barefoot through Chinatown after the assault was interrupted.

Detectives found a faded Mexican driver's license in the pants, but they could not say whether the license was genuine or whether the photo depicted the attacker.

The 22-year-old victim, who was on her way home from work, told police she was pulled into the subway entrance at Eighth and Race Streets and sexually assaulted about 9:30 p.m. Sunday.

"This male severely chokes the victim," said Capt. John Darby, commander of the Special Victims Unit. "She has obvious injuries."

The woman was treated at a hospital and released.

The subway entrance is across the street from Police Headquarters. A passerby who saw the assault was unsure if the woman was being attacked, but he called 911, Darby said.

The sirens of responding officers caused the attacker to leave the scene, without his pants.

"This male fled abruptly," Darby said.

Surveillance video showed the suspect darting across a parking lot and ducking under the mechanized gate at Ninth Street. Another video tracked him running to 10th and Spring Streets.

The driver's license found in the pants belonged to a 35-year-old man named Dario Gomez Lopez, from Puebla, Mexico. Detectives have been unable to find any police or other records of that person in the United States.

Although police do not know if Lopez was the attacker, Darby said, detectives are eager to see what he does know.

He said they have talked to the Mexican consulate and enlisted the help of multiple agencies in the effort to find Lopez.

The suspect was described as a Hispanic male, 5-foot-7 and 140 pounds. He had dark hair, and he was wearing a dark shirt, gray pants, and work boots.

Detectives are asking anyone with information to call Special Victims at 215-685-3251, -3252, or -3253, or to call 215-686-8477 (TIPS).

Contact staff writer Troy Graham at 215-854-2730 or tgraham@phillynews.com.