An environmental protest brought the U.S. Open women's semifinal match between American Coco Gauff and Czech player Karolína Muchová to a halt Thursday night, one game into the second set.

With Gauff leading 6-4 1-0, several people started shouting from the top section of Arthur Ashe Stadium, the largest tennis stadium in the world. The players eventually left the court and returned to the locker room as the protest continued.

According to tournament officials, three demonstrators disrupted the match. Two of them left quietly when security arrived but one of the protesters — who could be seen on social media posts wearing a shirt that said "end fossil fuels"— glued his feet to the floor of the stadium. Police were eventually called in and helped remove the final protester. 

The New York City Police Department later told CBS News a total of four people were removed from the stadium. 

The match resumed after a nearly 50-minute delay. It was not immediately clear what, if any, charges the protesters could face.

The protesters' shirts appeared to bear the logo of Extinction Rebellion, a group that engages in protests to demand action on climate change. During the protest, the group shared a story on social media about men's semifinalist Daniil Medvedev saying "someone is going to die" at this year's tournament because of the extreme heat. 

"At one tournament or another, it's inevitable, without significant change," the group wrote.

The New York City chapter of the group shared a statement that said in part: "The climate and ecological crisis threatens everything on our planet, including sports. This action and similar actions are the response of a movement that has no other recourse than to engage in unconventional means of protest to bring mass attention to the greatest emergency of our time."

It was the latest in a recent series of protests at sporting events —and tennis, in particular— related to the use of fossil fuels.

At Wimbledon in July, two matches were interrupted when environmental activists jumped out of the stands at Court 18 and scattered orange confetti on the grass.

At a U.S. Open tune-up tournament in Washington last month, about a dozen people were asked to leave the site after chanting and displaying signs protesting the use of fossil fuels.

Gauff, 19, is the first American teenager to reach the U.S. Open semifinals since Serena Williams in 2001. Muchová, 27, was also playing in her first U.S. Open semifinal. Gauff would go on to win 6-4 7-5 for a spot in the finals.

Another American, Madison Keys, was set to face off against Belarus' Aryna Sabalenka in the second semifinal of the night at the conclusion of the Gauff-Muchová match.