A police decision not to lay criminal charges over the Mangatepopo canyoning tragedy has dismayed the families of the six Auckland Elim Christian College students and teacher who lost their lives, principal Murray Burton says.

The seven were swept to their deaths following a flash flood during an outdoor adventure course at the Sir Edmund Hillary Outdoor Pursuits Centre (OPC) near Turangi in April last year.

Police last night released a statement saying their investigation into the tragedy was complete and they found no evidence of criminal offending.

"Police have met with the families of those who died and have also informed the OPC of the outcome of the police investigation."

They declined further comment as an inquest is to be held by Hastings coroner Christopher Devenport. No date for that has yet been announced.

Those killed were teacher Anthony McClean, 29, of Howick, and students Natasha Bray, 16, of Pakuranga; Portia McPhail, 16, of Manurewa; Huan (Tom) Hsu, 16, of Farm Cove; Anthony Mulder, 16, of Howick; Floyd Fernandes, 16, of Howick, and Tara Gregory, 16, of Mt Wellington.

Mr Burton said today he school did not want anyone to face criminal charges but was still hoping accountability would come from within the outdoors sector to ensure the same mistakes weren't repeated.

"I wouldn't say [the families were] disappointed but probably dismayed as to how sometimes the law does work against you rather than for you."

The OPC was fined $40,000 and ordered to pay reparations of nearly $500,000 in March after pleading guilty to charges laid under the Health and Safety in Employment Act.

It admitted it failed to take all practicable steps to ensure the safety of employee Jodie Sullivan, the instructor of the group, and that it failed to take all practicable steps to ensure no action or inaction of Ms Sullivan harmed any other person.

The Department of Labour said the OPC should have known from the heavy rain on the day that the group should never have entered the gorge, even though the water levels were not high when they entered.

The OPC should also have either subscribed to Met Service's weather warning service, or kept an eye on its website for weather warnings on the day of the tragedy.

By doing so it would have picked up three severe weather warnings the day of the tragedy, the department said.

Mr Burton said no amount of money could replace the loss of the children.

"[The families] would like to see significant and positive changes made within the industry that would go some way towards ensuring that maybe this won't happen again."

He acknowledged that without criminal charges, the industry may not be pushed into action.

Mr Burton said he hoped the coroner would make strong recommendations following the inquest.

"That's another very good opportunity to see if we can make some positives out of this tragic situation."