Police have named the worker who was killed when a South Auckland tank explosion blasted him across the road and into a car park.
Huntly man Jamey Lee Bowring, 24, died in the massive explosion at Salters Cartage in Wiri, and another man was injured.
Police and WorkSafe NZ investigations into the incident are continuing, and the death has been referred to the Coroner.
Witnesses say Mr Bowring, from Huntly-based company Race Works Ltd, was flung from the top of the tank, across the road, and into a car park.
They say he was welding when the explosion happened.
New Zealand Welding Centre senior welding engineer Alan McClintock said that if this was correct then it was the biggest welding accident that had happened in New Zealand.
Mr McClintock said the blast was a tragedy.
"Occasionally there have been unfortunate accidents with smaller things like drums, petrol tanks associated with vehicles - that sort of thing on a small scale.
"It's a big unpleasant surprise to see it happening on a large tank," he said.
Mr McClintock's organisation gives input into welding standards both in New Zealand and internationally, as well as guidelines which are in use in this country.
He said welding around fuel tanks, known as hot work, is high-risk but it became a low-risk activity if well-established safety procedures were properly followed.
Mr McClintock said there had "obviously been a breakdown" in safety systems, and added "probably more than one party hasn't followed the well-established safety guidelines".
"The first thing is an assessment has to be done by a responsible person who would be the owner of the premises or a delegated representative.
"This involves checking if there is any risk or any hazard, and if there is, putting in place procedures to make sure this sort of thing couldn't happen," he said.
Mr McClintock said these protocols were very detailed.
"There's two basic ways of making it safe - one is to remove anything there that is a potential fire or explosion hazard, the other way is to make sure there's no air or oxygen present.
"The safest method is to make sure it [the tank] is properly cleaned to make sure that nothing is in there," he said.
A representative from Race Works Ltd said last night it would not be able to comment until today.
Businesses assess damage after blast
Salters Cartage describes itself as an industry leader in New Zealand's hazardous recycling disposal market.
On its website, the company says it is a "one-stop disposal service" for waste oil from major oil companies, and for the shipping and automotive industries.
The company says it is also the contractor for Auckland Council's oil recycling initiative, in which recycled oil is collected from drop-off bins around the region.
It says it collects about 6500 litres each week from these locations.
In June, the company said its Bolderwood Place depot had undergone a major upgrade.
Concrete was laid across the whole yard and tank storage was increased by another 450,000 litres, to reach more than 2,000,000 litres of on-site storage.
The upgrade also included 24-hour live monitoring which checked levels in the tanks every five minutes.
Businesses surrounding the hazard disposal facility were today assessing the damage it caused to their own properties.
The top of the gas tank was still on grass about 40 metres from the building. Around it were several pieces of debris, including large orange frames that had landed on several cars.
Ross Taylor, the director of nearby Summit Aluminium, said the noise was so loud he thought something had crashed into his office.
"The noise was pretty horrendous really. The whole building shook. All the roof tiles bounced up." Mr Taylor said structural checks would be carried out on the building.
'Every worker should be able to return home safely'
The Engineering, Printing and Manufacturing Union said Salters Cartage was a non-union work site.
However, it said in a statement to Radio New Zealand that the union had an interest in workplace health and safety.
"We are thinking of the workmates and family of the deceased worker at this sad and stressful time.
"No matter the circumstances, every worker should be able to return home safely at the end of every shift.
"We urge WorkSafe to conduct a thorough investigation."