Walkout at SA hospital building site

Construction workers at the new Royal Adelaide Hospital site have walked off the job after another mishap involving cranes.

Workers concerned about safety issues walked off on Friday morning and won't return until Monday.

SafeWork SA said it was notified of an incident on Thursday when a load of steel, being moved by a tower crane, came free and fell to the ground.

"Inspectors commenced investigating the incident and Prohibition Notices were issued preventing the load of material being moved until a safe work method was developed," SafeWork said in a statement.

It said it was the sixth notifiable incident involving tower cranes in 2014, while there were seven in 2013.

More than 1000 workers are employed at the site, which operates 24 hours a day.