LUETZERATH, Germany (AP) — German police on Friday continued the clearance of a village that is due to be demolished to accommodate the expansion of a coal mine, with activists still holed up in one building, in tree houses and a tunnel.

Ahead of a demonstration to be held nearby on Saturday, Swedish climate campaigner Greta Thunberg visited the tiny village of Luetzerath and took a look at the neighboring Garzweiler open coal mine. Joined by others, she held up a placard demanding: “Keep it in the ground.”

Luetzerath has become a flashpoint of debate over Germany’s climate efforts.

The operation to evict climate activists holed up in the village kicked off on Wednesday morning, with some stones, fireworks and other objects thrown at advancing officers but no major violence. Most of the protest was peaceful.

Police started clearing the last occupied building on Friday, and police said that some other activists would then have to be taken down from tree houses, German news agency dpa reported.

There were also two activists in a tunnel. Regional police chief Dirk Weinspach took a look at the shaft and decried the risks they were taking, dpa reported, but he said he didn’t believe there was any acute danger to them. He said specialized rescuers would have to bring them out.

Environmentalists say bulldozing the village to expand the Garzweiler mine would result in huge amounts of greenhouse gas emissions. The government and utility company RWE argue the coal is needed to ensure Germany’s energy security.

Some protesters have complained of undue force by police and others said the scale of the police response, with officers brought in from across the country and water cannons on standby, was itself a form of escalation not justified by the peaceful protest.

The regional and national governments, both of which include the environmentalist Green party, reached a deal with RWE last year allowing it to destroy the abandoned village in return for ending coal use by 2030, rather than 2038.