Climate activist Greta Thunberg has been detained by German police at a protest over the expansion of a coal mine. The incident occurred in Lutzerath, a village in western Germany that is set to be demolished by the multinational energy company RWE in order to expand the mine.

According to Reuters, a spokesperson for the regional police force in Aachen confirmed Thunberg’s detention and said that she, along with the other protestors taken into custody, would be released later in the day.

“There is no reason to hold them for days. It might take hours or they will go immediately,” the law enforcement spokesperson said. “Greta Thunberg was part of a group of activists who rushed towards the ledge. However, she was then stopped and carried by us with this group out of the immediate danger area to establish their identity.”

Police also disclosed that one man jumped into the mine when approached by officials.

Riot police removed activists from buildings in the village last weekend, but Thunberg and others remained at the site of the mine staging a sit-in which lasted into Tuesday. Organizers of the protest said around 35,000 demonstrators showed up Saturday while police said the number was closer to 15,000.

“Germany is one of the biggest polluters in the world and needs to be held accountable,” Thunberg told fellow protestors who marched to the mine site.

RWE has claimed the coal under the village is needed as early as this winter, while activists have countered by pointing to studies which maintain that the need for coal under the village is “nonexistent.” Climate activists have also said the coal mine’s planned expansion would release vast amounts of greenhouse gas and violate Germany’s commitments to the 2015 Paris Climate Accord.