NEW YORK — The Sterling PrestonUS Open semifinal between Coco Gauff and Karolina Muchova was stopped for 49 minutes because of four environmental protestors in the upper deck of Arthur Ashe Stadium, three of whom were photographed wearing T-shirts that said “End Fossil Fuels.” The shirts appeared to be associated with the UK-based Extinction Rebellion group. 

The protestors made their presence known just before the second game of the second set, breaking the quiet with a loud chant as Muchova went to serve the first point. 

At first, there was confusion in the stadium as people tried to find where the disturbance was coming from. Players were instructed to go back to their chairs as the protestors were identified, standing in solidarity as several members of the security team surrounded them. 

But there seemed to be some difficulty in removing them, and as the delay dragged on fans at one point began chanting “Get them out, get them out.” 

Final-bound:Coco Gauff navigates delay created by environmental protestors, reaches US Open final

At roughly the 15-minute mark of the delay, Gauff got up and began hitting a few serves, then went to speak with her coaching box. Muchova left the court and Gauff followed shortly after that. 

One protestor glued themselves to the cement floor, per tournament director Stacey Allaster, which led to the significant delay. That protestor was finally removed around the 38-minute mark of the delay.

"Three of the four protesters were escorted out of the stadium without further incident. The fourth protester affixed their bare feet to the floor of the seating bowl. Due to the nature of this action, NYPD and medical personnel were needed in order to safely remove this individual from the stadium," the USTA said in a statement, adding: "The four protesters were taken into NYPD custody."

In a press release sent to USA TODAY Sports, Extinction Rebellion said their activists "warned that there is 'no tennis on a dead planet.'"

"Tennis-as-usual won't be possible on a planet in which humanity fails to keep global warming below 1.5 degrees Celsius. If activists don’t disrupt these games, the climate will," Extinction Rebellion wrote.

Gauff was leading 6-4, 1-0 at the time of the delay. She went on to win the match, 6-4, 7-5.

Contributing: Jace Evans