The body of an apprentice construction worker who fell to his death on a construction site at Perth’s Curtin University has been retrieved from the wreckage.

The 23-year-old, named by Perth media as Jonnie Hartshorn, died after falling more than 20 metres when a metal structure supporting the glass roof of a building collapsed on Tuesday afternoon.

Another worker also fell 20 metres. He had surgery for serious injuries on Tuesday and remained in a critical condition at Royal Perth Hospital on Wednesday.

A third worker inside the building at the university’s Bentley campus was also injured after falling about 10 metres.

Western Australia Police said that worker was conscious and able to speak. Both injured men are in their 20s.

Construction workers at the scene on Tuesday afternoon. Photo: Getty

Overnight, WA police and emergency crews retrieved the body of the dead man after using specialised equipment and calling in engineers to declare the building safe to enter, the West Australian reported on Wednesday.

A WorkSafe investigation is underway into why the building roof collapsed.

Electrical Trades Union WA organiser Damian Clancey witnessed the collapse, which happened during a lunch break.

He said there could have been many more deaths and injuries had it happened just five minutes earlier.

CFMEU state secretary Mick Buchan said he’d been made aware after the incident of issues with “deflection in the structural steel”.

“Those issues were addressed by structural engineers … [but] I understand that there were some concerns,” he said.

“It’s 2020. These events should not occur in the building and construction industry.”

The building will house Curtin’s new architecture school.

Construction began in 2019 and was due to be completed next year.

Head contractor Lend Lease was “deeply saddened” by the incident, according to a statement from the head of its domestic building division executive Dale Connor.

Mr Hartshorn worked for ABS Facade, a commercial cladding installation and glazing company with offices across the company, according to his Facebook page.

-AAP