Federal authorities have beefed up security at three wildlife refuges in the region amid the ongoing armed occupation of a sister refuge in eastern Oregon.

Additional officers have been sent to the Klamath Basin National Wildlife Refuge Complex that straddles the Oregon-California border, to the Ash Meadows National Wildlife Refuge in Nevada and Modoc National Wildlife Refuge in northern California.

Jody Holzworth, a regional spokeswoman for the U.S. Fish and Wildlife Service, says there have been no specific threats against those refuges and the agency just wants to ensure the safety of employees and visitors.

Meanwhile, there were no signs the last four occupiers at the Malheur National Wildlife Refuge are about to give up.