An engineer's report says shoddy construction led to the collapse of Stadium Southland in a severe snow storm nearly two years ago.
The report was commissioned by the Department of Building and Housing and carried out by structural engineer Dr Clark Hyland.
The department's chief executive, Katrina Bach, has referred the findings to the police and the Department of Labour.
The report says the September 2010 snowstorm was a one in 250 year event, but the stadium fell well short of safety standards and the roof should not have failed.
It shows shoddy construction methods were used when the stadium was built. It confirms that remedial work to fix sagging roof trusses discovered during construction in 1999 was inadequate and the welding was either missing or not up to standard.
Much of that work occurred on site, after a late design change during the building of the stadium.
The report says the substandard work could easily have been picked up at the time during the regular building inspections.
The department's deputy chief executive, David Kelly, says the number one focus of the New Zealand building code is life safety.
"This building, the inspection has found, was not up to those requirements in terms of safety."
Mr Kelly says it is extremely lucky no one was in the stadium when it collapsed.
Ms Bach is recommending all public buildings of similar design be fitted with snow load alarms.
Report unbalanced - builders
Amalgamated Builders, which built the stadium and is also building the new one, says the original design should have been identified as the fundamental cause of the collapse.
The company's director, Bruce Middleton, says while his company was the main contractor, it didn't design, make or erect any of the remedial work.
Amalgamated Builders has issued a statement saying the report is unbalanced and lacking vital information.
Noel Fitzgerald, who owned Aorangi Steel at the time the welding work in question was done, also takes issue with the report and says the work was done according to the plans.
He says the department's report was lacking in information and he blames the design for the failure of the building's roof and not his team.