A crane operator has been killed in a fall at a construction site in Melbourne's CBD this morning.
Several workers reportedly went to his aid but were unable to resuscitate him.
The construction workers' union says the man was a well-known and much-loved workmate.
Workers at the scene of the accident and at other Grocon sites across Melbourne stopped work as a sign of respect for the dead man.
Grocon chief executive Daniel Grollo has refused to provide any details of the accident, describing it only as a "tragic incident".
"Our sincerest thoughts and condolences go out to the family and to co-workers who worked with the individual, who is now deceased," he said.
"[It's] obviously a terrible event.
"As a sign of respect, Grocon has closed its sites across Victoria today pending an investigation and we'll update things in the morning."
Victoria Police and WorkSafe are investigating.
Ian Forsyth, the executive director of health and safety for WorkSafe, says it is too early to speculate on what happened.
"I think it just underlines the need for workplace safety. It's too early to speculate as to what may be the circumstances or the details of this untimely death," he said.
Mr Forsyth says a decision will be made later today on whether the site could be reopened on Tuesday.
"Immediately following an incident like this the site is preserved. It's not disturbed. We'll undertake that investigation," he said.
"We'll make a decision today as to whether that particular area needs to be still in its pristine condition or whether work could commence on this site."
Friend and fellow worker Tim White says it is a shocking loss of life.
"He was a quality man [who] comes from a quality family," he said.
"No-one [saw] what happened. A couple of young blokes up on the gantry [saw] him climbing up, but no-one saw him fall."
Construction, Forestry, Mining and Energy Union Victorian branch secretary John Setka says the man's death has hit his co-workers hard.
"Workmates... are going through a shocking time at the moment, as will the family and that's our main concern at the moment," he said.
"The investigation itself will continue and hopefully we will have some answers in the next few days, if not next few weeks."
The accident occurred at the site where .
Members of the Construction, Forestry, Mining and Energy Union (CFMEU) blocked the site in a week-long protest as they fought for representation on worksites.