NEW YORK (AP) — The U.S. Open semifinal between Coco Gauff and Karolina Muchova was delayed by 50 minutes because of a disruption by environmental activists in the Arthur Ashe Stadium stands on Thursday night. One protester glued his bare feet to the concrete floor.

Gauff was ahead 6-4, 1-0 when play was halted early in the second set. 

Security guards and, later, more than a half-dozen police officers went over to confront the three protesters, who were wearing shirts that read, “End Fossil Fuels.” Two of the activists were escorted out within several minutes, but it took longer to remove the person who stuck his feet to the ground.

Spectators were asked to move away to clear a path for the police, who were cheered by fans sitting near the section where the disruption happened. 

Gauff sat on her sideline bench for a bit during the break in the match, eating fruit out of a plastic container, before then getting some tennis balls and hitting a few practice serves. Muchova was briefly visited by a trainer during the interruption.