Initial inquiries into the Stadium Southland collapse show it was built when roof weight-bearing requirements were lower than they are now, Building and Construction Minister Maurice Williamson says.

Mr Williamson visited Invercargill today because a freak snow storm caused the stadium's roof to collapse under the weight of the dense snow on Saturday.

He told NZPA that elderly locals had told him they hadn't seen a snowfall like it in the city during their lifetimes and that roofs had also buckled or collapsed on several other buildings in the area.

The snowfall was a "spectacularly unusual" weather event, he said.

At the time the stadium was built in 2000, the building code for buildings of the stadium's nature sitting at sea-level was 0.323 kilopascals and that it was in fact designed to withstand 0.400kPa. A pascal is a measure of force per unit area.

However, there was evidence to suggest the weight of Saturday's snow may have been at that extreme or greater.

Mr Williamson said in 2006 a severe snow storm which damaged roofs in Canterbury had led to weight bearing requirements in the Building Code to be lifted to 0.630kPa for structures of Stadium Southland's stature.

"What I understand is that had that building been built under today's code, it would have survived."

Mr Williamson said some calculations had been done using information from Niwa about how much snow was likely to have been on the roof and found the weight would have been between 0.380kPa and 0.470kPa.

"The inquiries that are being run may find some other things that were either not done properly, or whatever, but that would be speculation."

He said an inquiry was being run by the company which set up the stadium's trust, and that council and government engineers were also looking into the collapse.

The demolition process on the site was under way and Mr Williamson said the people of Invercargill clearly wanted the 2000-seat stadium rebuilt as soon as possible.

The stadium cost about $10 million to build and was fully insured.

- NZPA