The Rest And Be Thankful road in Argyll and Bute is to remain shut after landslips left 75 ton boulders hanging over the carriageway.
Operators closed the route on Tuesday morning after around 2,500 tonnes of debris reached the catch-fences above the road following heavy rain.
A 60-mile diversion has been put in place while Bear Scotland works to clear the A83 and the alternative diversion along The Old Military Road below the main route.
Engineers inspecting the area say there are three large boulders at risk of slipping further down the slope onto the road.
The biggest is thought to be around 75 tonnes and is sitting 300m above the road surface. Engineers are working to secure the boulders by drilling into the rock and inserting a device which will help break them into smaller pieces on the hillside.
The clear up operation comes as further bad weather is expected to hit Scotland on Friday.
“Yesterday’s landslips have caused a number of boulders to become exposed which is causing some concern, and we want to be as confident as possible that there will be no further movements of material or the boulders on the hillside before we open the Old Military Road as a diversion which sits below the A83 carriageway.
“Teams have worked throughout the day to clear around 150 tonnes of debris from the Old Military Road in preparation for the route to be used as an alternative local diversion route, however this will not be used until we are confident that the road is safe.
“After that, teams will then turn to emptying and securing the material caught above the A83 carriageway in the debris fences.
“We continue to thank the travelling public for their patience while we do everything we can to address yesterday’s landslips. We encourage road users to follow the diversion route via Dalmally or to find an alternative form of transport. We advise motorists to check ahead with Traffic Scotland for real-time journey information.”