Idaho Highway 95 will remain closed in both directions at Sheep Creek near Riggins, after a rockslide covered the road and left the remaining hillside too unstable to safely reopen the road.
The Idaho Transportation department early Sunday said crews were attempting to detour the road around the slide, and protect the detour from further rockfall with a temporary berm and containers.
Crews stopped work once a large crack at the top of the hillside became visible from below.
"The very nature of slides is unpredictable," Operations Engineer Jared Hopkins said in a press release.
"At this time, we're not sure when we will be able to open the highway, but we are continuing to conduct geotechnical surveys and tomorrow [Monday] will have experts on the slope to pry off any loose material and further analyze its condition."
Highway 95 has been closed at milepost 188 since Friday morning, when a large rock slide covered the road with boulders as large as 25 feet in diameter.
There is no easy detour. Travelers can re-route through eastern Oregon and eastern Washington, but are discouraged from attempting to use unmaintained forest service roads in the area.