Motorists are facing a 59-mile diversion after a landslip led to the closure of the A83 at the Rest and Be Thankful.
More than 1,000 tonnes of material tumbled onto the road overnight, east of the area covered by debris fences and catchpits.
BEAR Scotland said its staff are on site assessing the situation on the A83 and will begin clearing the debris when it is safe to do so.
A diversion has been put in place via Crianlarich, Tyndrum, Dalmally and Inveraray, a distance of 58.8 miles.
Experts are assessing the Old Military Road on Thursday morning to decide if it safe to use to use as a diversion.
Eddie Ross, BEAR Scotland’s north west manager, said: “Safety is our top priority and 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.
“As ever, we thank the local community and road users for their patience, and assure them we’re doing everything we can to address the landslip at the Rest and Be Thankful as quickly and safely as we can.
“We remind road users that Argyll remains open for business and rest assured we’re doing everything possible to ensure the A83 opens as soon as it is safe to do so.”
He advised road users should to check Traffic Scotland for the latest information.