A St John Ambulance spokesman said four ambulances and a rapid response unit were sent to the scene the scene.
A neighbour described a "giant crash" and lots of people lying on the ground.
Despite the collapse, people on other balconies at identical units continued jumping, while others remained beneath the structures. She said more people flocked to the party, to see what the commotion was about.
A report conducted by the Ministry for Business, Innovation and Employment to investigate the cause of the collapse and whether the balcony was designed and constructed to the required standards found the number of people gathered on the balcony was the primary cause of its collapse.
It was noted that homeowners needed to be aware of the load their balcony was designed to hold and take responsibility during large gatherings or special events where excessive loading might occur.
Further to this, the report stated the construction of the balcony didn't contribute to the collapse.
Design standards had changed since the balcony was constructed, the report stated, and the sizes of supporting timber beams required for the type of structure had been increased in 2011.
"It is therefore now less likely that a similar balcony built to current standards would collapse if it were subjected to the same level of overloading," it said in the executive summary.
Inspector Jason Guthrie of the Otago Coastal police unit said police would not be laying charges.
