A worker at the Marischal Square construction site is facing disciplinary action after a forklift was crashed into a fence last week.
Building firm Morgan Sindall has said the machine was used without the proper certification on last Monday.
It happened just days after another incident at the site, when a worker suffered a broken leg and two broken ribs.
A spokesman for Morgan Sindall said: “On Monday a forklift truck collided with fencing, within the site boundary.
“There was no crane involved, nor any cars or members of the public.
“The worker operating the forklift did so without the proper certification and the appropriate disciplinary proceedings have been initiated.
“We operate a zero tolerance approach to unauthorised use of machinery across all of our sites. Safety is our number one priority and while incidents like this are extremely rare, they are completely unacceptable.”
Worker faces disciplinary action after Marischal Square incident