Federal officials said Sunday that no federal wildlife employees were in danger after a group of armed activists and militiamen protesting the prosecution of two ranchers took over a remote federal wildlife refuge in the rural southeastern corner of Oregon over the weekend.

A building at the refuge seized on Saturday afternoon by the group houses the offices of the Malheur National Wildlife Refuge, and is operated by the United States Fish and Wildlife Service, about 30 miles southeast of Burns, in Harney County. A representative of the Fish and Wildlife Service said the agency was monitoring the situation. “While the situation is ongoing, the main concern is employee safety and we can confirm that no federal staff were in the building at the time of the initial incident,” the press officer said.

The occupation began after a demonstration on Saturday in support of Dwight Hammond, 73, and his son Steven Hammond, 46, who were to report to California prison after a federal judge ruled that the sentences they had served for arson were not long enough under federal law.

Among the occupiers were Ammon and Ryan Bundy, two sons of Cliven Bundy, a Nevada rancher who became a symbol of anti-government sentiment in 2014, according to The Oregonian.