North Yorkshire Council has started an investigation after the railings at the edge of the pedestrianised area under Knaresborough viaduct collapsed down the river bank.
The council says it has made the area safe but the walkway will remain closed until repairs can be carried out.
They closed a section of the road at Waterside as a precaution, and expect to reopen it soon following further assessments.
More details will be issued when they are available.
Meanwhile safety checks were carried out on the viaduct itself by Network Rail but the lines above are now open again with trains travelling across the historic structure as normal.
