They did not identify the person and said no charges have been filed.
Management at Fayetteville's Cross Creek Mall also said Wednesday that it's fully cooperating with the investigation.
Fayetteville police said its Special Victims Unit began looking into the incident after the 16-year-old went to a hospital in another county and said she was pulled into the bathroom around 7:30 p.m. Monday evening at the mall and assaulted.
Police have not released a description of the attacker. They also haven't said if she knew him or it was a random attack.
Anyone with information is asked to contact the Fayetteville Police Department at (910) 433-1856 or Crimestoppers at (910) 483-TIPS (8477).