A group of protestors advocating for the cessation of fossil fuels halted play during the first US Open women’s semifinal on Thursday night.

American Coco Gauff led Czech player Karolina Muchova 6-4, 1-0 when several spectators stood up and began chanting. Asked to leave by security, they initially refused, leading the roughly 23,000-strong Arthur Ashe stadium crowd to shout “kick them out.”

Officials suspended play and roughly a dozen law enforcement officers surrounded at least one protestor, who was escorted out in handcuffs at 8.42pm, almost forty minutes since the interruption started.

Gauff, the youngest US women’s player to make the US Open semifinals since Serena Williams in 1999, is searching for a maiden final berth at her home Grand Slam. In the second women’s semifinal, American Madison Keys takes on Australian Open champion and soon-to-be World No. 1 Aryna Sabalenka.