A suspicious box was found at about 1 p.m. near the 12th Street entrance to the Rene C. Davidson Courthouse at 1221 Oak St., sheriff's Sgt. J.D. Nelson said.
One room was evacuated near where the package was found because of windows in the room, Nelson said.
The sheriff's bomb squad responded, detonated the box and determined it was harmless, a deputy at the scene said.
Some streets adjacent to the courthouse were temporarily closed.
As of about 1:20 p.m., court employees were reentering the building and all entrances were expected to reopen shortly.