As investigations continue into last month's helicopter crash off the sub-Antarctic Islands, the commission leading it says it may take up to 18 months or more to complete.

The wreckage will be inspected as part of the various investigations into the incident, but the lead agency behind the investigation says it's not the most important piece of the puzzle.

Transport Accident Investigation Commission (TAIC) spokesman Simon Pleasants said TAIC gave Southern Lakes Helicopters permission to retrieve the wreckage because, at this stage, it was not as important as the evidence of the three men on board. Other evidence also included extensive interviews with the helicopter's owners and operators, as well as maintenance records, CAA inspections and reports.

However, the recovered wreckage, and any that may still remain on the sea bed, was under a protection order forbidding anyone from interfering with it without TAIC's express permission.

Mr Pleasants said it would be transferred to a secure technical facility in Wellington if TAIC believed it needed to go there, "but that decision has not yet been made".

Investigators are currently in the evidence collection phase, which Mr Pleasants said often lasted several months. 

That's followed by analysis, a draft report, consultation with stakeholders with a legally-defined interest in the incident, a final report, then its publication.

"That whole process takes 12, 18 months. Sometimes longer. We've got one that's at around about the three-and-a-half year mark at the moment," Mr Pleasants said.

While TAIC is the lead agency investigating the accident, CAA spokesman Blake Crayton-Brown said the CAA's Safety Investigation Unit was conducting a safety investigation. 

It was limited in scope to communications between the operator and Air Traffic Control and the equipment requirements for operating outside of the NZ Domestic Flight Information Region, he said.

Meanwhile, the southern region has been quick to donate to two separate fundraisers last week. 

More than $15,000 has been raised thus far from last Friday's Westpac Chopper Bike Ride from Queenstown to Invercargill.

Bike ride organiser Murray Heath said final counts of this year's fundraiser were expected in the next few weeks as riders were still collecting donations from sponsors, but so far the event's

Givealittle page has raised $15,600. All funds raised as part of the 235km bike ride will go to the Lakes District Air Rescue Trust (LDART).

The next night in Te Anau, a fundraising dinner held by the Rotary Club of Fiordland raised $20,000 to help replace equipment lost in the helicopter crash.

The event held at the Te Anau Club "exceeded expectations" according to club president Marie Galland.

Mrs Galland said most of the funds raised would go towards search and rescue services in Te Anau and the Lakes District area. 

Southern Lakes Helicopters operations manager Lloyd Matheson said they were incredibly humbled at the fundraising efforts and support from the community.

He said they would be holding a joint meeting with both the ambulance and water rescue services to find out what specifically needed replacing and what the funds raised would be spent on.

"We're not sure how we're going to utilise the fundraising but we're absolutely humbled over the support that's come about and the continuing offers from other organisations as well. It's great to see all that support coming out of the woodwork."