BURNS, OR -- The FBI is revealing more about what investigators have found at the Malheur National Wildlife Refuge, following the 41-day occupation by militants.

Two large trenches were dug on cultural grounds that contain artifacts. One of those trenches was reportedly used as an outhouse. Teams also found guns and explosives. Concerns remain that vehicles and buildings on the property might be rigged with explosives.

The FBI's Art Crimes Team is helping agents process the refuge, to make sure artifacts from the Burns-Paiute Tribe are properly handles.