"Mr Chan was greasing a crane as part of routine end of year maintenance when it appears he inadvertently activated a remote control unit he was wearing," a statement released today by WorkSafe New Zealand said.
"That caused the crane's boom to move towards the truck deck, crushing and fatally injuring Mr Chan."
WorkSafe New Zealand's programme manager for construction, Marcus Nalter, said Mr Chan's death was a preventable tragedy.
"The company did not have a proper plan in place to ensure that in-house maintenance work was done as safely as possible," he said.
Mr Nalter said there were at least two "simple steps" that could have prevented this death.
"...the crane's power take-off should have been turned off and workers should have been instructed not to wear remote control units during cleaning and maintenance work," he said.
"If such a regime had been in place and been observed then the crane would not have been able to move in the way it did.
"Heavy vehicles such as cranes are always a potential workplace hazard - but with proper planning and safety systems those risks can be managed."