A rock slide April 11 left a 300-foot pile of rubble as high as 30 feet on the road.
State Department of Transportation spokesman Roger Wetherell says officials are worried about a large rock slab at the top of the slide area.
He says the slab at first was thought to be stable but cracks and fissures have appeared to indicate it could fall and endanger workers below.
A geologist will make a recommendation on how to stabilize the slope.
Wetherell says he's not sure how long it will take to assess the threat and take steps to address it.
The rail line to Whittier was not affected. The Alaska Railroad started twice-daily trips between Whittier and Anchorage while the road is closed.
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