The dead worker is believed to have been working for a subcontractor on the site where groundworks only got underway in June.
A policeman tried to revive the man using CPR but he was pronounced dead at the scene.
A Rok statement said: “Everyone at Rok would like to express deepest sympathy to the family of our colleague who died in this tragic accident.
“We have taken immediate steps to close the site and will be providing support to any member of the team affected by this sad news.
“We would like to thank the outstanding police officers who administered CPR.
“We will now be working with the Police, Procurator Fiscal and Health and Safety Executive so the circumstances surrounding this tragic accident can be ascertained.”