An inquiry into a fatal school caving trip in Whangārei will focus on why it went ahead despite heavy rain and thunderstorm warnings, a former WorkSafe investigator says.

A Whangārei Boys' High student died on Tuesday when his outdoor education group became trapped in Abbey Caves.

Fourteen other students and two adults got out.

WorkSafe confirmed it had launched an investigation but declined to comment further.

Shenah Lintern's daughter was among six Northcote College students who got trapped for hours in the Waipu Caves in Northland in 2007.

The teens and their instructors eventually had to swim to safety in the dark, and all survived.

But Lintern said she felt little had changed since.

Abbey Caves were just 35km from those her daughter was stuck in.

"I'm angry because they didn't learn from 2007," she said.

"In 2007 they knew that there was bad incoming weather and they still went ahead with taking the kids down into the caves. And they've done it again... I'm dumbfounded."

WorkSafe helped develop the national caving safety guidelines which stated instructors should know how and when to cancel a trip.

This included knowing weather forecasts, the maximum safe water level and safe waiting areas, escape routes and how to get out if the water rose, the guidelines said.

A former WorkSafe investigator told RNZ the current inquiry would look at the school's decision to go into the caves despite the bad weather.

It would consider who made the call and what reassurances they had that the students would be safe.

Those working on the investigation would also scrutinise everything that lead up to that decision and would likely take a guide into the caves to look at the risks, the former investigator believed.

Whangārei locals were struggling to make sense of what had happened.

"There's a weather alert, and here's a school taking these children into these caves while this is going on. Someone's arse needs to be kicked. Big time," one said.

"Who are you going to blame? The poor headmistress? No way. She's just doing her job," another said.

"No doubt there'll be a lot of finger-pointing. They've just got to get through it, work it out, what went wrong and move forward on making better decisions," a third commented.

"It's just sad for the whānau at the end of the day, very sad."

Oparara Guided Cave Tours manager Jude Harrington runs an operation that takes visitors into Kahurangi National Park on the West Coast of the South Island.

"If we are concerned enough by heavy storm warnings the night before, we will actually cancel a tour rather than take the risk," she said.

"The most common practice is to go and assess it in the morning. There's a point on the track where if the water is flowing across the track, they simply turnaround and come back out and we cancel."

Harrington said safety was paramount and there were usually several people involved in making the call on whether or not to go ahead.

The size of the group going into the cave was also critical - both for safety and conservation, she said.

"We operate under a Department of Conservation concession, so they set the number of people that can go.

"Because of the sort of terrain we're dealing with and some of the viewing points within the cave, we have a restriction of eight guests plus the guide," Harrington said.

The national guidelines recommended a ratio of one caving instructor to six people if they were in moving water.

That was not the case for the Whangārei Boys' trip which involved an instructor, a teacher and 15 teenagers.

Lintern said she felt like no one took into account the aftermath of the situations where trips did not go as planned.

Her daughter, now 31, still suffered from crippling anxiety that began about a year after her ordeal in Waipu Caves.

"There was a lot of danger involved - she got out safely but it has affected her since then," she said.

"And that's what they don't take into account, that if something goes wrong these children are going to be permanently affected by it."

The Education Outside The Classroom (EOTC) guidelines on the Ministry of Education website state no qualification is needed to lead most outdoor activities, with the exception of rafting.

The guidelines, published in 2016, say an analysis of serious incidents found incompetent leaders and ineffective supervision were major contributing factors.