Traffic management has been installed along a stretch of the A67 after the edge of the road started to subside.
Previously the road closed following major landslip in 2013. It reopened again in 2015 after a £2.44M programme of repairs.
Darlington Borough Council is assessing the scale of the problem.
A spokesperson for Darlington Borough Council said: “Following a report from a member of the public, who suggested a possible landslip has occurred below the A67, we have had geotechnical experts visit and they advised that further monitoring and investigation should be undertaken.
“The traffic management that has been is installed is to enable repairs to broken kerbs that have been hit by HGVs, and to allow investigation to commence. We will ensure residents are kept informed of any remedial works that may be required.”
In 2015, the remedial work included soil nails and mesh facing to repair the slopes.
Ground investigations in 2013 revealed that the ground instability was caused by two separate active landslips that extend over almost a 400m length of the A67 embankment.
The ground movement also threatened a water main owned by Northumbrian Water, which worked in partnership with Darlington Borough Council to investigate the problem.