The A83 has been closed in both directions in Argyll after a landslip resulted in more than 1,000 tonnes of debris covering the carriageway.
BEAR Scotland said staff were at the Rest And Be Thankful and would begin a clearance operation when it was safe.
They said the Old Military Road, which runs parallel to the A83, was also being assessed to see if it was safe to use as a diversion.
Drivers are currently being advised to take a 60-mile diversion route instead.
BEAR said ferry options were also available to travellers via Western and CalMac Ferries.
The landslip is the latest to hit the area, which was covered by 3,000 tonnes of debris in October 2018. That incident resulted in the road being closed for nine days.
The latest landslip happened east of an area that is covered by debris fences and catchpits.
Eddie Ross, BEAR’s north west manager, said safety was their top priority.
He added: “We’re doing all we can to assess the slope and the extent of the debris from the steep hillside above the carriageway.
“The landslide is east of the normal landslide susceptible area, but is within the section of the A83 that we could use the Old Military Road. The Old Military Road will be assessed this morning to consider if it is safe to use. In the meantime traffic will be diverted via the A882/A85/A819.”
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BEAR Scotland said the standard diversion route was in place from the closure points Tarbet to Cairndow: – A82/ A85 / A819: Westbound turn right onto the A82 at Tarbet and follow the road until Crianlarich – turn left onto A82 and continue until Tyndrum – turn left onto the A85 and continue until Dalmally – turn left onto A819 and follow the road until Inveraray.
Thereafter follow permanent signing. Eastbound At Inveraray, turn left onto the A819 then follow the road until Dalmally – turn right onto the A85 and continue until Tyndrum – turn right onto the A82 and follow the road to Crianlarich – turn right onto A82 and follow the road until Tarbet. Distance: 58.8 miles.