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

Gauff, who went on to win 6-4, 7-5, 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.

Security guards and, later, more than a half-dozen police officers went over to confront the protesters, who were wearing shirts that read, "End Fossil Fuels."

The U.S. Tennis Association said three of the protesters were escorted out of the stadium without further incident, but it took longer to remove the person who stuck his feet to the ground.

The USTA added that NYPD and medical personnel were needed in order to safely remove that person and that all four had been taken into police custody.

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.

Later, both players headed toward the locker room as the delay continued. Gauff sat on a treadmill, a towel draped over her lap, while chatting with members of her team.

It is 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, a 19-year-old American, and Muchova, a 27-year-old from the Czech Republic, were both playing in the semifinals at Flushing Meadows for the first time.

Their match was the first of the evening. In the other women's semifinal, Aryna Sabalenka of Belarus rallied from behind to defeat Madison Keys, 0-6, 7-6 (1), 7-6 (10-5) and reach her first U.S. Open final. The Australian Open champion had been just 1-5 in Grand Slam semifinals, including losses the last two years in the round in New York.

The second-seeded Sabalenka will face Gauff on Saturday.

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