The US Federal Bureau of Investigation (FBI) has moved to contain the last four occupiers at the Malheur National Wildlife Refuge in Oregon.

WASHINGTON (Sputnik) – Last week, a total of 16 activists were indicted over the armed occupation of Malheur National Wildlife Refuge.

"At this time, the FBI has moved to contain the remaining occupiers by placing agents at barricades both immediately ahead of and behind the area where the occupiers are camping. Negotiations between the occupiers and the FBI continue. No shots have been fired," the FBI said in a Wednesday release.

The FBI has encircled the four remaining occupiers at the Oregon wildlife refuge. Agents in armored vehicles are demanding they surrender. — Les Zaitz (@LesZaitz) February 11, 2016

​Wednesday marks 40 days since a militia group led by Ammon Bundy seized the headquarters building of the wildlife refuge, which is operated by the US Department of the Interior, in protest over discriminatory US government land management policies and practices, which the activists claim contravene the US Constitution, as well as to highlight the jailing of two local ranchers for starting fires on federal land.

"It has never been the FBI's desire to engage these armed occupiers in any way other than through dialogue, and to that end, the FBI has negotiated with patience and restraint in an effort to resolve the situation peacefully. However, we reached a point where it became necessary to take action in a way that best ensured the safety of those on the refuge, the law enforcement officers who are on scene, and the people of Harney County who live and work in this area," Greg Bretzing, Special Agent in Charge of the FBI in Oregon, said as quoted in the Wednesday release.

According to the statement, on Wednesday, one of the occupiers rode an ATV (all-terrain vehicle) outside the barricades established by the militia at the Malheur National Wildlife Refuge. When FBI agents tried to approach the driver, he returned to the encampment.