A man followed a woman into a port-a-potty and sexually assaulted her during a Foo Fighters Concert at Wrigley Field in Chicago on Sunday night at around 9:30 p.m., Chicago police confirmed to Variety.

Police say the 23-year-old-woman was waiting in line for food when a man — described as white, about 5 feet 9 inches tall and between 40 and 50 years old — sexually assaulted her. She then went to enter a port-a-potty when the man followed her into the restroom and assaulted her.

The woman reported the incident and police were called before she was taken to a hospital by a private ambulance. Her assailant is currently not in custody. A source adds to Variety that the assault did not occur directly in the venue.

The Chicago Cubs provides security for all events and games at the stadium through a private contractor, and Cubs spokesman Julian Green told the Chicago Tribune they would be increasing security for Foo Fighters’ Monday night show and encouraged anyone who may have any information regarding the incident to report it to police.

“Guest safety is paramount at Wrigley Field and we take every opportunity to ensure our guests’ safety, including routinely reviewing our security protocols and procedures with police,” Green said.