Stadium Southland's collapse under heavy snow two years ago will be referred to police after an investigation cited shoddy workmanship and a failure to identify structural defects.

The investigation found the snowstorm on September 18, 2010 was severe, but the roof would not have collapsed had it been constructed to building standards of the day.

The stadium was built in 1999.

Department of Building and Housing deputy chief executive David Kelly said the department was referring the investigation's findings because "the degree of non-compliance was of such an extent that the police should be involved".

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It is also referring the findings to the Department of Labour and giving a copy to the Institution of Professional Engineers.

Invercargill Mayor Tim Shadbolt and chief executive Richard King declined to comment for legal reasons.

But the stadium's builders, Amalgamated Builders, said the finding was "unbalanced and lacking vital information".

Spokesman Bruce Middleton said he believed the collapse was triggered by failure of a column connection under snow load, not the remedial work cited by the DBH report.

"The report fails to balance its conclusions by questioning the original design," he said.