The Bureau of Alcohol, Tobacco, Firearms and Explosives is "working an active investigation" in a rural Meade County residential area a few miles west of Ellsworth Air Force Base, according to spokeswoman Ashlee Sherrill.
Between 15 to 20 law enforcement vehicles were parked in front of a home on Elk Vale Road between 225th and 224th Street/County Highway MC-2 on Thursday morning. There appears to be fewer than a dozen homes along the stretch of dirt road.
At least one military-style vehicle was seen leaving the scene, and at least one helicopter was seen flying in the area.
ATF is investigating along with local and state law enforcement partners, Sherrill said. She said she can't disclose anything about the investigation because the case is under seal by the U.S. Attorney's Office in South Dakota. She said more information should be available next week.
Business continued as usual at Ellsworth, which did not assist with the operation or go into any sort of security lockdown, according to spokesman Steven Merrill.