The accidental omission of the word thunderstorms by MetService may have been a factor in events leading up to the death of six students and a teacher on Tuesday.
Six students and a teacher were swept to their deaths when the river they were crossing was hit by a flash flood.
Water levels in the gorge rose 36 times in just half an hour, leaving virtually no chance of survival.
Questions are being raised about whether the Elim students should have gone into the river. Weather warnings were in place, yet officially there was never a suggestion that the fatal expedition in the Mangatepopo Stream south of Turangi would be called off on Tuesday.
The Edmund Hilary Outdoor Pursuit Centre is defending its decision to allow the expedition to head out despite poor conditions, saying they had not received alerts.
And MetService says the word thunderstorms was accidentally omitted from the Tongariro forecast between midnight and 6.30am.
The correction was made just 16 minutes after the Outdoor Pursuits Centre received its faxed forecast. But the manager of the National Forecasting Centre, Peter Kreft, says a correction was issued at 6.32am and that was the version the Outdoor Pursuits Centre should have received by fax a short time later.
He says then at 8.30am it issued an explicit severe weather warning and Kreft says regardless, the first forecast said there would be heavy rain falls.
ONE News spoke to individuals who had been anxious about the torrential rain and gusts but most OPC staff were too distressed to talk on Wednesday after a sleepless night comforting colleagues and bereaved family members.
The centre says it is difficult to get weather information in the field because it is so remote.
CEO Grant Davidson said they were overcome with shock and disbelief but that they were nevertheless showing care and compassion for the families involved.
"It's absolutely tragic. I feel for them and also for the families." he told ONE News.
The group was canyoning in the gorge when the weather suddenly turned. The teens were wading, walking and helping each other across waterfalls.
But there are questions about whether notices about impending heavy rain were heeded.
On Monday afternoon, the MetService city forecast supplied to ONE News predicted rain, heavy and thundery falls, and gusty northwesterlies in Taupo and Tokoroa for the following Tuesday - the day the school party headed out into the stream.
MetService says a weather warning was put out at 8:29am on Tuesday.
Forecast manager Peter Kreft says that particular warning included explicit mention that people needed to be aware of rapidly rising rivers and streams, as a consequence of very high hourly rainfall rates expected in some areas.
But Davidson says this was not a matter of MetService's warning not being heeded.
"We just didn't receive the information. We subscribe to a met fax service so we can brief our staff at eight o'clock, and the fax released to us at 6.15am had none of that information on it."
Up to 5,000 students take part in the centre's courses each year. But previously there had only been two deaths, the last in 1987.
The man who established the centre, adventurer Graham Dingle, says it had concentrated on safety.
"I think you could say that in my day it was quite high-risk, but OPC have done a lot to make it safe, and I don't think you could say it's high-risk any longer. The people who are the instructors at OPC are the best in the world, and certainly OPC sets a benchmark for safety."
The centre has now opened its own investigation into the accident and Elim school principal Murray Burton says he is waiting for the results while supporting grieving students, staff and parents.
"We have natural questions as to what decision-making process they went through, and that'll be good to find that out. That's where I will leave it at this stage."
Inquiries are expected to take months to complete.
With school holidays coming up, the Outdoor Pursuits Centre remains closed. Two school groups have been sent home and the staff and management will deliberate on Thursday over when to re-open to student groups. The Palmerston North coroner is to conduct a full inquiry into the cause and circumstances of the seven deaths.
The police and department of labour will investigate the incident and the Outdoor Pursuits Centre will conduct its own investigation.
