A union says two safety representatives have been dismissed from the new Royal Adelaide Hospital worksite after a crane incident last Friday.
All eight cranes stopped work after the load on one got out of control and hit a handrail.
Six cranes now have been cleared to resume operation.
CFMEU official Aaron Cartledge said two workers had been unfairly dismissed.
"These would make five safety reps in all that we have found have some way been removed off the project and it's becoming quite a trend and endemic that when a safety rep really has a strong voice that somehow they run foul with management and are removed from the site," he said.
Mr Cartledge said talks had been held with management about the operation of the safety committee.
"We're trying to work with management to resolve it, our members are unhappy about it," he said.
"We do want these latest two safety reps reinstated on the project while we work through the grievance procedure as per the agreement that we had with management."