A Transport Accident Investigation Commission inquiry found that molten material ejected by gas-cutting activities on the ship very probably ignited dry sawdust or wood shavings, creating a fire which spread to other flammable materials in the hold.
Tong and his company K R Tong Ltd employed the gas-cutters, who were removing metal braces which had kept the cargo in place on the ship's voyage from China, where the wind turbine components had been loaded.
Tong appeared in the court for sentencing on a single charge of exposing an individual to a risk of harm, laid under the Health and Safety at Work Act 2015.
Judge Gordon Matenga reserved his decision on the sentence Tong would face. The Act provides for a fine.
The judge said he hoped to be able to issue his judgment before Christmas.
The man considered the victim in the case was one of Tong's employees, whose name was suppressed.
Maritime NZ originally laid the charge alongside another of failing to comply with a duty, which was later withdrawn.
Tong's company K R Tong Engineering Ltd faced the same two charges, but the charges against the company were also withdrawn.
Maritime NZ counsel Sarah Henderson said Tong was not on the ship at the time the fire broke out, but his culpability was based on his responsibility as an officer of his company, not as a worker.
He should have made sure his staff were better prepared, she said.
Defence counsel Alistair Darroch said there were wood shavings in the hold below where the gas-cutters were working, and the standard of "housekeeping" there was "terrible".
He said Tong had safety systems in place, but the workers on-site made the decisions, as Tong was not there.
A foreperson conducted a job analysis and was told Tong's staff could not go below, where it was pitch black. Covid-19 restrictions were in place, which meant they could not talk to the crew.
A critical decision could have been made to withdraw from the job when the workers were told they could not put a fire spotter below, but they continued.
"The workers are doing their best, and they make the wrong decision," Darroch said.
However, Tong was not blaming the workers for what happened.
"A very serious fire has taken place, and Mr Tong accepts responsibility for not getting that right," Darroch said.