The anti-government militia broke into the U.S. Fish and Wildlife Service building in Oregon on Saturday. The group’s leaders said they are ready to stay for years. The Federal Bureau of Investigation said it is working to bring the occupation of the wildlife center “to a peaceful resolution.” The U.S. Fish and Wildlife Service said its staffers are all safe. But it said on its website that the center is closed until further notice.

The group says it acted to protest prison sentences given to two cattle farmers. A court found Dwight and Steven Hammond guilty of setting fire on federal land in Oregon. The ranchers had used the land used for grazing by their cattle. The group posted a sign at the occupied center that accused the government of abusing its power.

“We will be here as long as it takes,” said Ammon Bundy, a leader of the occupying group. He said the group has no plan to use force against anyone. But he said, “If force is used against us, we would defend ourselves.”