Police will not lay charges after 18 people were injured when a balcony collapsed at a concert held at at flats in Dunedin last year.

Photo: RNZ / Ian Telfer

The balcony of a flat in Castle St collapsed due to overloading when Six60 performed a free concert in March last year.

A 19-year-old woman suffered severe spinal injuries, one man fractured both his legs, and others were left with neck and head injuries.

Police today released the the findings of their investigation.

Otago Coastal area commander Inspector Jason Guthrie said police had found no criminal wrongdoing and would not be laying charges.

"The findings of the investigation were reviewed by the police's legal team and no criminal liability was found," Mr Guthrie said.

"On the afternoon of 4 March 2016, an event was held on private property with the attendance of a professional band," he said in a statement.

"The number of people on one of the balconies fluctuated from about 9 people to some 18 or so at the point the balcony collapsed.

"The balcony was not intended to hold more than 8 people.

"Despite original reports that people were jumping up and down on the balcony, the video footage shows this was not the case."

Photo: RNZ / Ian Telfer

Mr Guthrie said neither the construction of the balcony, nor the materials used, contributed to its collapse.

A report by the Ministry of Business, Innovation and Employment in August 2016 found the balcony's construction met standards, but it was not designed to hold 18 people.

The University of Otago also investigated the matter and found failings in the event's organisation had led to overcrowding.

Mr Guthrie said police would continue to work with the university, Dunedin City Council and other agencies to "ensure we do not see a repeat of such an incident".

"Police's thoughts remain with those affected by this incident and support continues to be provided," he said.