A construction worker in his 50s is in intensive care after being crushed at the building site of the new Royal Adelaide Hospital.

The circumstances of the man’s injury have yet to be determined, but his union says he suffered a head injury while working in the basket of a scissor lift early this morning.

Work on the site has been suspended for the day.

The construction union’s state secretary, Aaron Cartledge, said the worker had started a shift at 6am and had been found injured by fellow workers at 7.15am who tried to assist him until paramedics arrived.

No-one witnessed the accident on level two of the new building on North Terrace.

“Our thoughts at this stage go out to the family,” Cartledge said.

“A lot of guys knew this worker – he’s been in the industry some time. He’s very popular on the site. There’s a lot of guys that are devastated.”

The head of the construction project, Peter Salveson, said SA Police and SafeWork SA were investigating.

“The circumstances of the incident were quite traumatic in terms of particular people who were supporting him on site, and they’re being offered counselling at the moment,” he said.

A meeting of all workers was held and it was agreed that everyone should leave the construction site.

Earlier, SafeWork SA’s Bryan Russell told ABC radio that the man sustained a serious crushing injury to the head, neck and back while working on a scissor-lift work platform.

The circumstances are still unclear, with early reports that the man had suffered a heart attack.

Workers leaving the site weren’t sure what had happened to the man.

“The only thing I’ve heard is that this is a lift accident – that’s it,” one worker told InDaily.

Another said he believed the man had been caught between a scissor lift and a concrete step.

He said the workers would return at 7am tomorrow to find out more.