Authorities say the incident happened in the 2000 block of East Avenue J-8 around 6:15 a.m. Investigators say the teenager thought she was being followed, so she crossed the street, but the suspect followed.
According to police, the suspect dragged the victim into the bushes and sexually assaulted her. The man fled the location on foot and was last seen heading toward 20th Street East.
The victim went to a nearby home for help and contacted police. She was taken to a local hospital for treatment.
The suspect was described as a black male, 30 to 35 years old, 5 feet 7 to 5 feet 8, with dreadlocks.
A $5,000 reward is being offered for information that leads to an arrest. Anyone with information is urged to call the L.A. County Sheriff's Special Victims Bureau at (877) 710-5273.